A new edition of the 'Debian Administrator's Handbook' is available for free to download [0], and free to browse online [1], thanks to Raphaël Hertzog and Roland Mas.
There's also a paper version with a 25% discount until Sunday [2].
[0]
Epub: https://debian-handbook.info/download/jessie/debian-handbook.epub
Mobipocket: https://debian-handbook.info/download/jessie/debian-handbook.mobi
PDF: https://debian-handbook.info/download/jessie/debian-handbook.pdf
[1] https://debian-handbook.info/browse/jessie/
[2] http://www.lulu.com/shop/rapha%C3%ABl-hertzog-and-roland-mas/the-debian-administrators-handbook-debian-jessie-from-discovery-to-mastery/paperback/product-22408803.html