The Simple The Original Series Reading Lists are just my subjective versions of several condensed suggested reading lists, depending on the number of  books you might want to get.  Below are the top ten, twenty, thirty, forty, and fifty The Original Series novels you should read.

CLICK HERE FOR THE FULL READING LIST.

Top Ten Five Year Mission Novels

  1. The Captain's Oath
  2. Constellations
  3. Crucible: Provenance of Shadows
  4. Crucible: The Fire and the Rose
  5. Crucible: The Star to Every Wandering
  6. Federation
  7. The Entropy Effect
  8. Prime Directive
  9. The Eugenics Wars, Volume One
  10. The Eugenics Wars, Volume Two

Top Ten Movie Era Novels

  1. Ex Machina
  2. The Final Reflection
  3. Mere Anarchy
  4. D.T.I.: Forgotten History
  5. Spock's World
  6. Rihannsu: The Bloodwing Voyages
  7. Rihannsu: The Empty Chair
  8. Strangers From the Sky
  9. To Reign in Hell
  10. Sarek
Twenty Novel Version
(With Focus on the Five Year Mission)

  1. The Captain's Oath
  2. Constellations
  3. Crucible: Provenance of Shadows
  4. Crucible: The Fire and the Rose
  5. Crucible: The Star to Every Wandering
  6. Final Frontier
  7. Federation
  8. Legacies: Captain to Captain
  9. Legacies: Best Defense
  10. Legacies: Purgatory's Shadow
  11. From History's Shadow
  12. The Entropy Effect
  13. Assignment: Eternity
  14. The Face of the Unknown
  15. The Latter Fire
  16. Prime Directive
  17. Yesterday's Son
  18. Allegiance in Exile
  19. The Eugenics Wars, Volume One
  20. The Eugenics Wars, Volume Two
Twenty Novel Version
(With Focus on All Eras)

  1. The Captain's Oath
  2. Constellations
  3. Crucible: Provenance of Shadows
  4. Crucible: The Fire and the Rose
  5. Crucible: The Star to Every Wandering
  6. Federation
  7. The Entropy Effect
  8. Prime Directive
  9. The Eugenics Wars, Volume One
  10. The Eugenics Wars, Volume Two
  11. Ex Machina
  12. The Final Reflection
  13. Mere Anarchy
  14. D.T.I.: Forgotten History
  15. Spock's World
  16. Rihannsu: The Bloodwing Voyages
  17. Rihannsu: The Empty Chair
  18. Strangers From the Sky
  19. To Reign in Hell
  20. Sarek
Thirty Novel Version
(With Focus on the Five Year Mission)

  1. The Captain's Oath
  2. Constellations
  3. Errand of Vengeance: The Edge of the Sword
  4. Errand of Vengeance: Killing Blow
  5. Errand of Vengeance: River of Blood
  6. Errand of Fury: Seeds of Rage
  7. Errand of Fury: Demands of Honor
  8. Errand of Fury: Sacrifices of War
  9. Crucible: Provenance of Shadows
  10. Crucible: The Fire and the Rose
  11. Crucible: The Star to Every Wandering
  12. Final Frontier
  13. Federation
  14. The Vulcan Academy Murders
  15. The IDIC Epidemic
  16. Uhura's Song
  17. Legacies: Captain to Captain
  18. Legacies: Best Defense
  19. Legacies: Purgatory's Shadow
  20. From History's Shadow
  21. The Entropy Effect
  22. Assignment: Eternity
  23. The Face of the Unknown
  24. The Latter Fire
  25. Prime Directive
  26. Yesterday's Son
  27. Allegiance in Exile
  28. A Contest of Principles
  29. The Eugenics Wars, Volume One
  30. The Eugenics Wars, Volume Two
Thirty Novel Version
(With Focus on All Eras)

  1. The Captain's Oath
  2. Constellations
  3. Crucible: Provenance of Shadows
  4. Crucible: The Fire and the Rose
  5. Crucible: The Star to Every Wandering
  6. Federation
  7. From History's Shadow
  8. The Entropy Effect
  9. Assignment: Eternity
  10. The Face of the Unknown
  11. Prime Directive
  12. Yesterday's Son
  13. Allegiance in Exile
  14. The Eugenics Wars, Volume One
  15. The Eugenics Wars, Volume Two
  16. The Lost Years
  17. Ex Machina
  18. The Final Reflection
  19. Mere Anarchy
  20. D.T.I.: Forgotten History
  21. Spock's World
  22. Rihannsu: The Bloodwing Voyages
  23. Rihannsu: The Empty Chair
  24. The Higher Frontier
  25. Living Memory
  26. Strangers From the Sky
  27. Time For Yesterday
  28. To Reign in Hell
  29. Sarek
  30. Cast No Shadow
Forty Novel Version
(With Focus on the Five Year Mission)

  1. The Captain's Oath
  2. Constellations
  3. Errand of Vengeance: The Edge of the Sword
  4. Errand of Vengeance: Killing Blow
  5. Errand of Vengeance: River of Blood
  6. Errand of Fury: Seeds of Rage
  7. Errand of Fury: Demands of Honor
  8. Errand of Fury: Sacrifices of War
  9. Crucible: Provenance of Shadows
  10. Crucible: The Fire and the Rose
  11. Crucible: The Star to Every Wandering
  12. Final Frontier
  13. Crisis of Consciousness
  14. Federation
  15. The Vulcan Academy Murders
  16. The IDIC Epidemic
  17. Uhura's Song
  18. The Case of the Colonist's Corpse
  19. Legacies: Captain to Captain
  20. Legacies: Best Defense
  21. Legacies: Purgatory's Shadow
  22. Ishmael
  23. From History's Shadow
  24. The Shocks of Adversity
  25. The Entropy Effect
  26. Assignment: Eternity
  27. The Face of the Unknown
  28. The Latter Fire
  29. That Which Divides
  30. Agents of Influence
  31. Prime Directive
  32. The Antares Maelstrom
  33. Yesterday's Son
  34. Allegiance in Exile
  35. A Contest of Principles
  36. The Eugenics Wars, Volume One
  37. The Eugenics Wars, Volume Two
  38. Troublesome Minds
  39. No Time Like the Past
  40. The Rings of Time
Forty Novel Version
(With Focus on All Eras)

  1. The Captain's Oath
  2. Constellations
  3. Crucible: Provenance of Shadows
  4. Crucible: The Fire and the Rose
  5. Crucible: The Star to Every Wandering
  6. Final Frontier
  7. Federation
  8. Legacies: Captain to Captain
  9. Legacies: Best Defense
  10. Legacies: Purgatory's Shadow
  11. From History's Shadow
  12. The Entropy Effect
  13. Assignment: Eternity
  14. The Face of the Unknown
  15. The Latter Fire
  16. Prime Directive
  17. Yesterday's Son
  18. Allegiance in Exile
  19. The Eugenics Wars, Volume One
  20. The Eugenics Wars, Volume Two
  21. The Lost Years
  22. Ex Machina
  23. The Final Reflection
  24. Mere Anarchy
  25. D.T.I.: Forgotten History
  26. Spock's World
  27. Rihannsu: The Bloodwing Voyages
  28. Rihannsu: The Empty Chair
  29. The Higher Frontier
  30. Living Memory
  31. Strangers From the Sky
  32. Time For Yesterday
  33. To Reign in Hell
  34. Excelsior: Forged in Fire
  35. Best Destiny
  36. Sarek
  37. The Captain's Daughter
  38. Vulcan's Forge
  39. The Lost Era: The Sundered
  40. Cast No Shadow
Fifty Novel Version
(With Focus on the Five Year Mission)

  1. The Captain's Oath
  2. My Brother's Keeper: Republic
  3. My Brother's Keeper: Constitution
  4. My Brother's Keeper: Enterprise
  5. Enterprise: The First Adventure
  6. Constellations
  7. The Janus Gate: Present Tense
  8. The Janus Gate: Future Imperfect
  9. The Janus Gate: Past Prologue
  10. Errand of Vengeance: The Edge of the Sword
  11. Errand of Vengeance: Killing Blow
  12. Errand of Vengeance: River of Blood
  13. Errand of Fury: Seeds of Rage
  14. Errand of Fury: Demands of Honor
  15. Errand of Fury: Sacrifices of War
  16. Crucible: Provenance of Shadows
  17. Crucible: The Fire and the Rose
  18. Crucible: The Star to Every Wandering
  19. Final Frontier
  20. Crisis of Consciousness
  21. Federation
  22. The Vulcan Academy Murders
  23. The IDIC Epidemic
  24. Uhura's Song
  25. The Case of the Colonist's Corpse
  26. Legacies: Captain to Captain
  27. Legacies: Best Defense
  28. Legacies: Purgatory's Shadow
  29. The Rings of Tautee
  30. A Choice of Catastrophes
  31. Ishmael
  32. From History's Shadow
  33. The Shocks of Adversity
  34. The Entropy Effect
  35. Assignment: Eternity
  36. The Face of the Unknown
  37. The Latter Fire
  38. That Which Divides
  39. Agents of Influence
  40. Prime Directive
  41. The Antares Maelstrom
  42. Yesterday's Son
  43. Allegiance in Exile
  44. A Contest of Principles
  45. The Eugenics Wars, Volume One
  46. The Eugenics Wars, Volume Two
  47. Troublesome Minds
  48. The Weight of Worlds
  49. No Time Like the Past
  50. The Rings of Time
Fifty Novel Version
(From All Eras)

  1. The Captain's Oath
  2. Constellations
  3. Errand of Vengeance: The Edge of the Sword
  4. Errand of Vengeance: Killing Blow
  5. Errand of Vengeance: River of Blood
  6. Errand of Fury: Seeds of Rage
  7. Errand of Fury: Demands of Honor
  8. Errand of Fury: Sacrifices of War
  9. Crucible: Provenance of Shadows
  10. Crucible: The Fire and the Rose
  11. Crucible: The Star to Every Wandering
  12. Final Frontier
  13. Federation
  14. Legacies: Captain to Captain
  15. Legacies: Best Defense
  16. Legacies: Purgatory's Shadow
  17. From History's Shadow
  18. The Entropy Effect
  19. Assignment: Eternity
  20. The Face of the Unknown
  21. The Latter Fire
  22. Prime Directive
  23. Yesterday's Son
  24. Allegiance in Exile
  25. The Eugenics Wars, Volume One
  26. The Eugenics Wars, Volume Two
  27. The Lost Years
  28. Ex Machina
  29. The Final Reflection
  30. Mere Anarchy
  31. D.T.I.: Forgotten History
  32. The Wounded Sky
  33. Spock's World
  34. Rihannsu: The Bloodwing Voyages
  35. Rihannsu: The Empty Chair
  36. The Higher Frontier
  37. Living Memory
  38. The Pandora Principle
  39. Strangers From the Sky
  40. Time For Yesterday
  41. To Reign in Hell
  42. In the Name of Honor
  43. Excelsior: Forged in Fire
  44. Best Destiny
  45. Sarek
  46. The Captain's Daughter
  47. Vulcan's Forge
  48. The Lost Era: The Sundered
  49. Cast No Shadow
  50. Vulcan's Heart