Books like Dungeons & Dragons Fifth Edition Monster Manual
Christopher Perkins, Mike Mearls, Jeremy Crawford
Dungeons & Dragons Fifth Edition Monster Manual is 352 pages, about 6 hours 27 minutes at 250 words a minute.
How long Dungeons & Dragons Fifth Edition Monster Manual takes to read
6 books to read next
How long each takes
Dungeon Master's Guide 5.9 h Volo's Guide to Monsters 4.1 h 
Sword Coast Adventurer's Guide 2.9 h 
Xanathar's Guide to Everything 3.5 h 
Shadowdale 6.2 h 
Baldur's Gate II 4.5 h Bar height shows length. Estimated at 250 words a minute.