Re:FYI (Score 2, Informative)

SourceBeat has been offering "subscription" based eBooks for a while now. My book Desktop Java Live just had its first release published through them. The books are updated often to keep up with changes in open source content. SourceBeat also supports print on demand so ordering a print copy generates the latest version available. This gives readers the best of both worlds regardless of whether they pick the eBook or the print version.