First off, the place is difficult to find. Go to 726 builidng，and enter the entrance under the arch thing between the two banks. Turn right, and take the elevator to the 7th floor.
The museum is quite small, but we'll stocked. There are a couple of hundred posters perhaps to look at.
But, if you are a history nerd like myself, the gift shop is the star of the show. Original posters from the 60s... Original copies of the little red book in various languages, busts of Mao, old maps, old textbooks, old magazines... This place is a treasure trove, and will satisfy history buffs from a tiny budget of ¥150 for three copies of posters, to over ¥6k for rare originals, and everything in between.