This is worthy reading, O’Reilly’s latest bookscan analysis State of the Computer Book Market, Part 1 shows sustained growth in the technical book market over the last year, and he includes a treemap that shows the relative growth of a variety of categories.
Most noteworthy, according to Tim’s analysis, is that sales seem to be growing for the bestsellers but there is less growth in the backlist, and Tim notes that with growth concentrated in bestsellers, publishers seem to be trimming their title count. This is certainly true for a couple of houses that have undergone some relatively public reductions in title count.
As to which sort of books are doing well these days, Tim suggests that references (a la Java in a Nutshell) have been hit hardest by the web, but notes that O’Reilly at least is seeing growth in the tutorial market (books that can’t easily be replicated online).
Definitely worth reading, I’ll link to Part 2 when he posts it.