The Campbell-Kelly and Aspray book is defintely the best overall history, and I use it in my own courses. Another overall history, more technical in general and stronger on Unix and minicomputers, is Paul Ceruzzi's "A History of Modern Computing." If he's interested in the early Univacs, then the detailed book to get is "A Few Good Men from Univac" by David E. Lundstrom -- out of print, but Amazon has it used. There's a ton of books on IBM, but for a good mix of technical and business, he might like "Building IBM: Shaping an Industry and Its Technology" by Emerson W Pugh.
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I put together a list of key resources in the history of computing for a recent NSF backed workshop on using history to teach computer science better . It has books as well as some links to history sites and other resources. People interested in this topic might also want to check out the site for my computer history and culture course at Colby College -- the pages for each session include additional links and readings." Hackers was one of the main texts -- it's a great book, but more recent. (I posted something anonymously -- sorry to duplicate. I got myself an account now).