I’ve now purchased a couple of short cuts from O’Reilly: RJS Templates for Rails and Schematron. At $9.99 a pop, they seem to be pretty good value for money (especially with the current GBP to USD rate). Each one is around 50 pages, which is a concise enough to be a good introduction to a particular topic without going overboard.
They have a couple of (minor) faults. The biggest is that the PDFs don’t look that good in Preview.app, forcing me to install Adobe Reader. I haven’t looked into why it’s so bad yet. The other reason is the lack of chapter breaks. The books feel like one continuous block of text (aka a Terry Pratchett novel).
I did notice one or two typos in the Schematron book, but I’ve reported them and hopefully, the PDF can just be regenerated. Yay ebooks!
As to the topics covered, both RJS and Schematron are subjects which are too small to be covered by a full book (200+ pages) yet deserve more attention than a single web article might give it. They’re ideal for this format.
Overall, I’m pretty pleased with these. I’ll likely be going back for more.