They do it every 24 hours, at some point in the evening Toronto time.  And have been doing it for at least six months - I think that's how long I've been checking.  They tend to release the previous revision of a book rather than the current one, so the content tends to be a couple years out of date.  Sometimes that's very important, sometimes almost meaningless depending on the subject.  I find it's useful to check Amazon reviews of the books - Packt isn't as picky about their quality as O'Reilly is.  But some of them are quite good, and the topics, while all "technical," have varied wildly.  And it's hard to argue with the price.

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