Max Allan Collins has a good series of detective novels wherein his fictional schamus, Nate Heller, gets involved in real historical mysteries and provides solutions to them based on his reading of the historical facts. The first book, True Detective, is excellent. The second, True Crime, involving John Dillinger and Ma Barker, is fun but a bit of a stretch as to the solidity of its conclusions. The third, The Million-Dollar Wound, is possibly the best thing Collins ever wrote, and ends up providing a very convincing case that Frank Nitti did not commit suicide.

The one that covers the Lindbergh kidnapping is fascinating because it is so uneven. It goes deep into how utterly botched and weird the official investigation and conclusions were, but it also provides a "solution" that requires to believe that Edgar Cayce was genuinely psychic (without which, Heller would never have found answers in the case), and that the Lindbergh boy not only lived, but to at least middle age. (The series got more desperate later on, including one book that "solves" an assassination by pinning it on a composite character, rather than a real historical figure. And the Amelia Earhart book is a damn good book, with a damn ridiculous read on history.)