There is only a catch on this offer: it’s only available in Spanish. What a good opportunity for practicing your newly acquired skills!!
Contrary to what happened in the classroom, the book provides a detailed view of many cryptographic algorithms, including DES, IDEA, AES, RSA, ElGamal, DSA, … etc
Update: For those of you that still prefer a book written in English you can download this one. Though a bit aged it is still a very solid book.