I stayed for a few nights right before the summer season started so it was pretty chill but it was a nice time. The location is cool... outside the town but sort of like nestled in the woods. It's interesting. 2 minute walk from the beach... solid 20 minute walk from the town, though. The owners are very relaxed and friendly and will help you out with whatever you need or just hang out and chat.
I had a fine time at Macanudo. The rooms are big (and air conditioned!), the hostel itself is spacious and the roof is pretty neat. It's a pretty relaxed atmosphere and its easy to hang out with the other guests or just ride solo. The two owners are super friendly and the other employees were very nice/helpful as well. It really is a great spot if you are going to be in Montevideo. The breakfast could use some work, but that certainly didn't take away from a great experience.
My stay at Books was interesting. First night they messed up my room and I got woken up by the kid's bed I was in. Whatever, no biggie. The last night there I had the room to myself, I get home and one of the staff members or permanent residents or whatever is banging a girl in the room and had the door propped shut, tells me to F*$# off and come back in 15 minutes... Next morning a fight broke out between some staff members and some residents. Still had a fine time, but the place is sketchy.
Staff was super nice, the place was clean, breakfast was good, shower was hot, internet worked fine, they had adapters for my U.S. plugs... The only negative I can think of is that you can only do #2 in one of the bathrooms... sometimes I dont want to wait to do #2, you know what I mean?