Having been to the national museum at Siem Reap, the national museum at Phnom Penh can hardly compare. There are some Buddha sculptures and some relics at the place. Not much things to read on in the place. Would recommend skipping this and visiting the museum at Siem Reap, which has a better representation and summary of the Ang Kor history. Check out the killing fields and Tsol Seng prison at Phnom Penh instead.