[fjtorres]

Typically it is closer to 17% of *cover price* on tradpub hardcovers, about half of that on paperbacks. Retailer discounts typically run 40-45% so the publisher gets about double what the author (+agent) gets.
Tradpub ebooks it is nominally 25% of net so the publisher gets triple the author (+agent) take. Retailers seem to be getting 30% of the consumer price.

Buying ebooks direct from an author's website nets them 90%+.
Buying ebooks from a retailer nets the author/publisher 35%-65% depending on price and the retailer, most typically 65-70%.