I love Mozart and his late operas. There are many, many recordings of all of them, even of La Clemenza di Tito, readily available in separate releases these days. If you love them as I do, or if you have not heard them before, I cannot recommend any option more highly than this repackaging at an almost-embarassing-to-mention price of Gardiner's marvellous accounts. You will want to hear others if you like them, but of the versions I own or have heard (a lot!), I would unhesitating recommend these as an overall best buy, and as a single box they have no current competition I am aware of at the present time. I am not a stickler for period instruments, but I think where they are used, they lend a particular beauty to Mozart's work, especially in the balance of woodwind and string sonorities and this is very obvious throughout these performances. There are no libretti apparently (I have the individual releases where the booklets do include the words) but in Mozart's case this is far less of a problem than it might seem as you can no doubt find translations on the internet without too much bother!
Rene Jacobs' performances on Harmonia Mundi have received much praise, and are certainly enjoyable and fascinating. But they also have some irritating features, including overblown continuo playing, funny tempi where it really counts, and a sometimes rather thin string sonority that won't be to everyone's tastes (I do think his Zauberflote is more interesting than Gardiner's however, which has beautiful choral singing in particular, but is perhaps rather on the serious side....). Gardiner's singers are, by and large, more convincing too - the Don Giovanni is much, much better than the other period performance options and to my taste, the most exciting performance I've heard. Idomeneo is much better than Jacobs or, I'm sorry to say, Mackerras, and I think the Entfuhrung is more effective overall than the Christie recording. The Nozze di Figaro here is regarded by some as a bit serious, but I have to say a quick comparison recently of the first act in the Jacobs recording with this inclined me strongly to the Gardiner, in terms of orchestral sonority and vocal quality. There's some extraneous noise here as in Cosi, but you'll have to decide if it bothers you. It hasn't me. La Clemenza di Tito isn't so comprehensive in terms of how much recitative is included as Jacobs, but the tempi seem better to me and the singing is wonderful...
Frankly, even disregarding the compactness and price of this re-release, I don't think there is (currently) any better way of getting to know this, some of the most remarkable music for the stage anyone has ever written.