Big, expensive books with pretty pictures are nice, but they don’t engage your brain all that much. Consider some of these alternatives for your coffee table.
Tangram Puzzles: 500 Tricky Shapes to Confound & Astound Puzzles are always a good thing, and tangrams are great for improving those spatial skills. The shapes are challenging, but not impossible, to solve and since there are only seven pieces, you aren’t likely to lose any.
And finally, if you want to put food on your coffee table, I suggest mixed nuts that are still in the shell. This is a great snack because it is healthy, discourages mindless eating since you have to work to get the nut out of the shell, and engages the brain a bit since each nut is, in a way, its own small puzzle. Just remember the nutcracker and an extra bowl for shells.