There are thousands of magazines around and plenty of variety. However, when you like books and feel like reading informative articles, TLS is what you want.
I don't feel especially inclined to read the Times itself. To be honest, I probably read it no more than ten times in my life. On the other hand, the Literary Supplement, I always pick up with excitement.
More than learning things on a subject, it also revives knowledge you already have. It reassures you in your observations on which or which author or book. Another obvious side effect of reading TLS and, I think, its goal, is for us to read the books and works mentionned in the articles.
This way, thrugh this magazine, I took back my Oscar Wilde's works and biographies as an extensif article was written about the Duchess of Padua in the TLS of a few weeks ago.
If you enjoy british literature and actually many other, as TLS is far from being exclusif, do pick one up one day. It is just as good as buying a book of novellas.