Richard Dawkins and Douglas Adams.
From RD's Lament for Douglas, originally published in The Guardian in 2001:
"Douglas and I met because I sent him an unsolicited fan letter-- I think it is the only time I have ever written one. I had adored The Hitchhiker's Guide to the Galaxy. Then I read Dirk Gently's Holistic Detective Agency.
"As soon as I finished it, I turned back to page one and read it straight through again-- the only time I've ever done that, and I wrote to tell him so. He replied that he was a fan of my books, and he invited me to his house in London. I have seldom met a more congenial spirit..."
In The Salmon of Doubt, there's an interview with Douglas Adams "The book that changed me." He lists Richard Dawkins' The Blind Watchmaker.
Now, for the actual art, I don't like how the two came out so different from each other stylistically. I couldn't find any good pictures of Douglas Adams in profile, so I had to guess. -____-
But I really like the height difference between the two, since Adams was supposed to be over six feet, and Richard is so... I don't know. He always struck me as slightly delicate, or just under average size, but maybe it's all in my head, with his lovely soft voice in all....
Hope you guys spotted what books each of them are holding.