I have a friend who is begging for spanish catholic books.  Can anyone direct me?

Tell him to read Denzinger and the Roman Catechism, this is of course assuming he has gone through all of the Baltimore Catechism first.

After finishing those two, go over them again. After that I would recommend to simply read St. Thomas for different topics he might have questions to.

For spiritual reading, there are so many excellent books. The Imitation of Christ is a must read for anyone who wants to start on the path to perfection and abandonment. Another great thing to go over, is the sermons of St. Alphonsus Ligouri. They can be found on the blog of Radio Cristiandad, they read them with an excellent perfect tone and pitch in spanish. They are also on youtube, but just go to their website directly and have him check out the spanish audio stuff they have on the sermons of the Saints.

So first thing to do is first have him learn the faith, after learning the faith and having a strong foundation in dogma/doctrine. Then one can really start reading spiritual books with more frequency. The reason why I say this is a must for today, is that otherwise the anti-Christ doctrines of our day might take over. I would also recommend to re-read over and over all the anti-modernist encyclicals.

Satis cognitum, Pascendi, Humani Generis, Aeterni Patris, Mirari vos, Lamentabili Sane, Syllabus of errors etc... All of these are a must for someone to see clearly that the Conciliar Church is indeed an anti-Church.

Also make special note, that all private revelation that has been approved must be read according to the mind of the Church. So if you read something that seems doubtful, then your interpretation is wrong. There are two possibilities that this came from Satan, which is certainly possible. All true prophets have had false apparitions, this you can especially see when you have a second hand source etc... So take Anne Catherine Emmerich, there is some doubtful stuff in her writings, but if you read it with the sole purpose for pious reading and as aids to meditation on the Passion. I cannot argue against you, but if you read it with the purpose "of filling" in the blanks in the narrative with a sort of curiosity that public revelation was insufficient, then I would anathematize that practice.

Way too many good Catholics I know, have fallen astray into the weirdest cults/sects because of private revelation. So anathematize any non-Marian approved apparition before Vatican II. It is not worth the prize of your soul, especially during a time period, where false apparitions are going to multiply to no end.

Where can one purchase Spanish reading material, such as books?

I know there are some native Spanish speakers on this board but I can't remember their names right now, so you might get a larger response if you posted this in the General discussion area.  Surely all language groups have their equivalent of Tan Books or the likes of an Angelus Press.

Marsha