In general, I agree, but this is not always true. Some non-fiction books read very much like fiction. An example that I recently finished is
Endurance by Alfred Lansing, which tells the story of Ernest Shackleton's failed mission to cross Antarctica on foot in 1914 (they got stuck in the ice only a few miles from land and spent the next year and a half stuck drifting on the ice before making an escape attempt when they finally reached open water).
Lansing spent years doing research for this book, including interviewing all the living crew members, and it is 100% true. But it has a proper plotline, fantastic character development, and a very climactic and happy ending. Reading ahead won't exactly ruin the story (the basic points of the mission are commonly known anyway), but there's no advantage to doing so.
In other words, some non-fiction books are novels too, and they should be read like novels.
