Don't fear. The inertia from all the over the top action sequences where the reading marker drops through the stack of pages like through vacuum keeps you going through the heavier parts in no time.

Ps: Anathem > Seveneves, unless you ignore the last third. Stephenson is usually weak at the end, when all the pieces are put in place and there is no room left for brilliant tangents. Anathem suffered surprisingly little, Seveneves more than usual.