One in the clever "Royal Diaries" series by Scholastic, which pairs young-adult authors with famous princesses. The adolescent Isabel, exiled to Segovia by her brother the king, is primarily concerned with her impending marriage, which she hopes will be to Ferdinand of Aragon. The book is designed to feel like a real princess's diary, with gold-embossed pages and a sturdy binding.  (SPN187, $10.95)