Can't speak to either of the two that you mention, but I have heard high praise for the Bosch Automotive Handbook as one of the most up-to-date and comprehensive general guides. http://books.sae.org/book-bosch7

I'm sure from your starting point of the very basics, either or both would be quite useful. If you have a public library, I would say check them out there. Or buy the one that appeals to you more, and read the other from the library.

Based on titles alone, I'd go with Halderman, because Principles, Diagnosis, and Service sound like exactly what you want to know.