Short answer: sometimes. This is a little complicated, so bear with me:

When you look at the book in the library catalog, you'll see the call number listed. If next to the call number you see "**(LIB USE ONLY)**", that means the book is not allowed to leave the library, including overnight. If you do *not* see "LIB USE ONLY" there, it means that you can take it out overnight if you check it out less than two hours before closing; for instance, after 6:00 p.m. Mon.-Thurs. (See library hours.) It will be due one hour after the library opens the next morning.

For examples, take a look:

Some more details: We close at 5:00 on Fridays. This means that you can check a reserve book out after 3:00 on Friday, and it would be due at 10:00 am on Saturday (1 hour after we open.) We close at 3:00 on Saturdays and are closed on Sundays; so if you check it out after 1:00 on Saturday, it would be due at 8:30 am on Monday. And then there are holidays... When in doubt, ask a librarian!