I guessed it on day 3 but wasn't sure until day 8!
Day 3:
1. Absurdistan
2. Artemis Fowl
3. Bitter Fruit
4. Born to Exile
5. The Cardinal
6. Coastliners
7. Crystal City
8. The Cyberiad
9. The Darkling
10. Distant Star
11. The Diviners
12. Dreamtigers
13. The Drifters
14. The Exorcist
15. Face the Fire
16. Fingersmith
17. Firestarter
18. The First Man
19. Generations
20. The Grey King
21. Grim Tuesday
22. The Iron Heel
23. Lord of Light
24. Lost Horizon
25. Mental Radio
26. Mother Night
27. The Neutrino
28. Oliver Twist
29. The Outsider
30. Le Pre Goriot
31. The Prestige
32. Rabbit Redux
33. The Ragwitch
34. The Republic
35. Ride the Wind
36. The Risk Pool
37. Rogue Nation
38. Sir Thursday
39. South Riding
40. Straight Man
41. The Survivor
42. Tribal Scars
43. La Virevolte
44. Wartime Lies
45. Was It Murder
46. Wintersmith
47. Winter Wheat
48. Wyrd Sisters
49. The Yearling
The book title must consist of exactly
11 characters
and contain the following characters:
1 x 'R'.
1 x 'T'.
1 x 'I'.
Total matching book titles found: 49
Book titles with 11 characters..: 189
Total number of books processed.: 3910
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Day 7:
1. Artemis Fowl
2. Oliver Twist
The book title must consist of exactly
11 characters
and contain the following characters:
1 x 'O'.
1 x 'R'.
1 x 'S'.
1 x 'T'.
1 x 'I'.
1 x 'W'.
1 x 'L'.
Total matching book titles found: 2
Book titles with 11 characters..: 189
Total number of books processed.: 3910
And after the Day 8 letter there was only ONE!
"Es kann nur eine geben!" - Duncan McCloud