Always avoid brittle books. Structure is important but so is preservation, and a book with brittle pages is on its last legs in that department, unless there's a restorational method of reversing the deterioration. Normally (but not always) the book is very tan, with the browning visible on the cover, with some of the corners missing. If I wanted a reader, I'd obviously prefer one with decent pages so I could read the damn thing and not have to worry about damaging it - comics are fragile things, but brittleness is the point of no return for me, even with the best storage available. As for investment, I'll pass. Too much of a scarlet letter for me.