The library is an awesome resource. Aside from books, you can get free entry to museums, they have conference rooms and study spaces you can book, free subscriptions to ebooks, internet access, writing tools, betterment workshops, etc
I've seen a lot of posts lately saying that to support a library, you should get a card. Other things you can do:
1. Be promiscuous in using that card
2. Go to board meetings
3. Join the Friends
4. Demand the books that represent you, you can challenge absent books as much as present ones
5. Donate
Even better? Get a library card AND use it. How many places offer free information, free entertainment, free customer service with no expectation that you buy anything or leave a tip, and a free place to relax and chill with a good book?