By Jim Fisher. Probably the gold standard for books on the Lindbergh kidnapping; I don't entirely agree with the retired FBI agent's conclusions (or with the publisher's decision to file this primarily under "Jerseyana"...really, Rutgers Uni Press?) but you can't argue with his research.
If you want newer true-crime writing from Fisher, he has a blog (and it was updated the day I wrote this entry!). If you want a newer copy of this paperback, good luck; this one's straight from the publisher's warehouse.