Pennant Hills Library falls within the Hornsby Shire network of libraries (there are five in total). It's not as big as the Hornsby branch, which is the one I'm most familiar with and the central library for the Shire, but is not as tiny as one in Berowra either.
The library is located on the opposite side of Pennant Hills Station to Pennant Hills Road. It shares a building with Pennant Hills Community Centre, on the corner of Yarrara Road and Ramsey Road.
There's a pretty decent amount of books here. I'd say about half as many as there are at Hornsby. Quite a few times I've found ones that weren't available at Hornsby library.
The children's area here is particularly good, being quite large. I'm not just referring to the selection of books either, but also to the open space given to kids to use. There are chairs and mats, all in prime position overlooking Wollundry Park (which is great to visit with little kids).
Technology at the library is just as advanced as it is at Hornsby, with self checkout, computers and all the rest. The library is pretty much just a smaller version of the central library (which means there's no study rooms or anything).
Local groups like book clubs and knitting groups still use the space to meet (the latter holds events on Thursday mornings). Popular activities for kids like Bubs 'N Books (on Fridays) and Storytime for Preschoolers (on Tuesday and Wednesday) are also held.
I don't remember seeing it before, but the last time I was at Pennant Hills Library, inside the door there was a table of books for sale for ten cents each. The selection wasn't great, so I didn't get any, but 10 cents is almost free, so I recommend seeing if there's any available when you stop by too.
Toilets are located within the Community Centre. Just around the corner are the women's ones, and downstairs are the men's toilets.