John Sutherland points out that marriages are less than eternal, but a dedication lasts forever:

James Atlas, Saul Bellow’s biographer, records that to get his muse working the novelist liked to change wives. He got through five and his dedications are a trail of marital gore. His last great novel, Ravelstein, contains a vicious portrait of Mrs Bellow No 4 (Alexandra Ionesco Tulesca, Romanian physicist) and a fulsome dedication to Mrs Bellow No 5 (Janis Freedland, former student):

“A la bella donna della mia mente.

To Janis

The star without whom I could not navigate”

Luckily for Janis, if not for his fans, the old fellow died before he hitched his fiction to the next star.

In a 2003 article, Susan Johnson traced the changes of heart that showed up via the dedications page, and also discovered astonishing egotism:

Male writers are certainly capable of the most pompous dedications, though, and Ford Maddox Ford would be hard to beat. The famously ugly writer, who was astonishingly successful with a string of beautiful women (including a young and lovely Jean Rhys), wrote what must be one of the most self-regarding dedications of all time when The Good Soldier was re-issued: “My dear Stella, I have always regarded this as my best book, at any rate as the best book of mine of a prewar period; and between its writing and the appearance of my next novel nearly 10 years have elapsed, so that whatever I may have since written may be regarded as the work of a different man, as the work of your man. For it is certain that without the incentive to live that you offered me I should scarcely have survived the war period and it is more certain still that without your spurring me again to write it I should never have written it again. And it happens that, by a queer chance, The Good Soldier is almost alone among my books in being dedicated to no one: Fate must have elected to let it wait the 10 years that it waited, for this dedication … And so I subscribe myself in all truth and in the hope that you will accept at once the particular dedication of this book and the general dedication of this edition. Your F.M.F”

I have nothing but admiration–baffled admiration, but admiration notheless–for Jane Davitt and Tim Morgan, who have a page devoted to the dedications in Robert Heinlein’s books. One assumes tracking down the identity of the dozens of people mentioned in prolific SF writer Robert Heinlein’s dedications takes, well, a lot of dedication.

And here’s the McSweeney page of Random Book Dedications Read From The Bargain Bin.