Professional Plone Development - now an e-Book
Packt Publishing release a PDF e-book version of Professional Plone Development
By accident, I discovered that Packt are now selling an e-Book version of my book, Professional Plone Development. For a time, they halted the publication of e-Books due to piracy concerns. The good news is that the books are not seriously hampered by DRM. The PDF is encrypted with a password, and you can't copy its text electronically, but you can print, read and, crucially, search. The lack of copy-and-paste shouldn't be an issue, since the book's accompanying source code is more complete and easier to borrow from, and is of course not restricted in any way.
Packt do a bundle for about $40 where you can get both the dead-tree and the electronic version of the book, or you can buy them individually, for $36 (paper) and $23 (PDF), respectively.