Ronald Huereca has released the second edition of his book, WordPress and Ajax. The book itself is still PDF only, but the new edition brings new chapters like “Page Detection in WordPress”, “Nonces and the Escape API”, “Ajax Registration Form” and others. The new version also includes manually highlighted and tested code snippets.
WordPress and Ajax is temporarily only $14 (it’s normally $24). Of course if you’ve purchased the book in the past, the second edition release is a free update. There is also a preview of the book that tops out at about 60 pages if you just want a taste before purchasing.