Dave Thomas just announced a new Pragmatic Bookshelf series called Pragmatic Fridays. I have no idea what inspired the name "Friday" in this context, but a Pragmatic Friday is a short (60 - 100 pages), low-cost ($7.50 - $10), and focussed book on a specific topic. The books are available for download in PDF form only, and as with all downloadable Pragmatic Bookshelf titles, they contain no DRM.
The first Pragmatic Friday title Rapid GUI Development with QtRuby by Caleb Tennis is available for download now, at the price of $8.50.
I think this is a great idea. I thoroughtly enjoyed the Pragmatic Starter Kit books on version control, unit testing, and automation. At 150 to 200 pages, they were very readable and acted as a great tutorial on the respective subjects. They obviously did not cover all the details but provided enough of a foundation to enable the reader to easily dig deeper into the topics by using web resources, etc. I have a very low attention span when it comes to books, and these are one of the few books that I've actually read cover to cover. The Pragmatic Fridays seem to take this a step further by being more limited in scope, which I think has a great potential. And the $7.50 - $10 price point definitely seems very reasonable.
Other Pragmatic Fridays titles in the pipeline include "Ruby Best Practices", "Google Maps API", and "Preparing Rails Applications for Deployment". The Pragmatic Programmers are also accepting proposals, in case you are interested in writing a Friday yourself. This might be an interesting opportunity for would-be writers.