I've enjoyed the last couple books by the erstwhile cardinal, but if I remember correctly there is a joke or anecdote about German theologians that it seems I can confirm about Ratzinger - or, if I'm just making up a non-existent memory, maybe I'll formulate the anecdote myself: they talk about questions from a variety of angles but do not very often tell you how they would answer them.
Truth and Tolerance is a case in point. On the whole I think it's a helpful book. Either I'm just very dense, though (and I concede that this may be the case), or he doesn't really come right out and describe the relations of the two in the sort of explicit terms that I'd like to see. Maybe my expectations were just all wrong.
Or maybe my temperament is of just the wrong sort for German theology. I find the approach of Maritain and St. Thomas to be much more appealing: here is the truth, and here is where modern philosophy and world religions have got things wrong. But Ratzinger takes a different approach. Where I would say that the Enlightenment has for all intents and purposes been a trip down the wrong road, Ratzinger says that "we do not by any means need to bid adieu to the Enlightenment as such" (p. 256). I just don't agree. We've had 200 years of working out the consequences of the Enlightenment (and even longer if we include its humanistic precursors), and I'm not sure that we've got much to show for it: tens of millions dead in the atheistic embrace of Marxism, for one horrible example. Yet even if we set that aside, there are problems on the right-wing of the Enlightenment as well, as even Ratzinger concedes. He rightly rejects a "freedom" that consists in seeking to divorce oneself from any dependence or duty towards others: "An understanding of freedom is wrong if it would see as liberating simply an ever-widening loosening of norms and the constant extension of individual freedom in the direction of a total liberation from all order" (ibid). Man is made for community with God and others, and we dehumanize ourselves if we deny either of these essential aspects of what it means to be human.
Well, what then is there to preserve from the Enlightenment? I'm not sure, but then I'm no philosopher or theologian.
Anyway, Truth and Tolerance is a worthwhile book, and I commend it to you, but I'm going to have to stick with Maritain and St. Thomas myself.