I think the books are fine on one side and I might do a colorful modern art glass piece on the other side.

From what we can see in the photo, it looks more traditional then modern, but you have some lovely pieces. That is a very nice coffee table, beautiful wood and has what I would describe as "understated elegance". Style it simply in the same way. I would remove the tray, it's competing, too busy. Leave the books with something tall beside them. You can see how it looks with the books and the candle holder beside them, but I suggest a lovely vase instead. Here is a good reference pic for you, even same table!

DITTO!!!