Hi Manic Mary
My heavy hints are as follows
Title of the book (extra letters are in 1, 16, 23, 26, 29, 34, 37, 39, 41 Across and 1, 3, 4, 5, 6, 24, 29 Down
The instruction is C????E O?E L????R IN F???E C?????S
When you do this (leaving real words) and write the surname of the author in the barred off cells reading L to R, you get the 5 titles reading top to bottom in those columns. Column 1 title starts in row 2 (3,7), Column 4 title starts in row 2 (6), Column 7 title starts in row 1 (9), Column 10 title starts in row 3 (10) and Column 13 title starts in row 2 (8) N.B The column 13 title is the ENGLISH version of the name of a title character.
16 Ac (3,6) Think Russian rather than German authors.
The instruction letters are calculated by adding the "score" of the missing word's initial letter to the "score" of the solution's initial letter.
e.g. 8Ac
missing word = black = 2
solution = Ace = 1
2+1 = 3 = C