Anywhere between a book a day and a book a month (with occasional extreme outliers in either direction), depending on work pressure, nuisance from small child, etc. The ready availability of reading matter on the internet -- interesting but mostly unimportant, coming in small digestible chunks, the reading equivalent of fast food -- has a pernicious effect on the amount of real reading I do.

Definitely worth it. Probably worth it even in purely financial terms since some of what I read is job-related, but the main reason is that I (1) enjoy reading and (2) have omniscience as a primary goal in life.

I usually have several books on the go at once. The two I had open most recently are Chris McManus's "Left hand, right hand" (a book about asymmetry, especially in human beings; recommended) and Peter Winkler's "Mathematical mind-benders" (a selection of mathematical puzzles ranging from tricky high-school level to harder-than-IMO; highly recommended to those who like such things).