Please accept my apologies for contravening the rules by beginning a duplicate thread, put it down to unfamiliarity, now I know I will adhere to them.
As for my original reply:
I kept looking at the last two words of 1d, - could it be "I say"?, ""I can"?, "O The"? etc etc, then it clicked into place. In the '70s I worked in a library technical services department, and we handled a lot of his books, so the rest of the theme was relatively easy. I remember my boss complaining "my children can't tell what kind of animals they're supposed to be".
Only one I have left is 17d (Geronimo for instance eaten by lions), I have h-r-/ g-e-, any hints appreciated.