I just found out about this so I thought I'd pass it along: It appears the creators of Varnish
have created a for-profit venture "Varnish Software"
to market Varnish as a service, and as part of that effort they wrote an e-book, The Varnish Book
. One of the challenges with Varnish has always been the lack of thorough "how-to" documentation, so this is good news.
(See my December post, Making sense of Varnish caching rules