I've got all four, and so far I've read all of them except for the book on hops. Am I crazy?
I take a fix the problem approach to by beer, so I focus on whatever I feel is the greatest fault first. Initially I had lot of odd flavors that I attributed unhappy yeast, so I tackled the yeast book first. Still don't have complete control of my fermentation temps, but learned enough from the book that I've sorta got a handle on the problem.
Next up: malt and water. Read these at about the same time, while trying to get a basic understanding of mash chemistry. Still a lot more that I could learn from these books, but that'll have to wait till my night classes finish up...