VMware publishes pretty comprehensive tech docs (e.g. SDK & API), which I'd always prefer over a written/published/printed book since they are (probably) more up to date and contain less errors.
Having said that I also know that it is sometimes easier to learn from paper, so you could either print those documents or buy a book off of Amazon.
I'd probably buy the one that has the best reviews. I know, not really greatest recommendation but unless there are a bunch of profound 0-star reviews the number of reviews and overall rating is a great indicator if that book actually helped people or not.