Totally. The cost of the book is often so much less than the cost of the time spent reading it (am assuming a developed country's perspective here). So one should optimize for the time rather than the cost of ownership of the book.

I have a huge library of books (and I have read many of them), and still find pressing topics I need to know which are not covered by any of the books I have (and neither seemingly by the Internet at least till I discover some relevant keywords).

An additional thing is that I have read through the introductions of a lot more books, and that by itself gives a first understanding of the subject.