At the beginning of the year, I started putting out some nuts on my windowsill to attract any hungry birds. Living in the middle of the city, not much came around. But eventually a few magpies became frequent visitors and picked them up regularly. I began to see them more often in the trees in front of my house and after a while, they began to build one of their huge, domed nests right across the street in plain view of my living room window. It was pretty dang awesome to see the whole thing live. Especially knowing that I, as a reliable food source throughout the end of winter and then spring, probably was at least part of the reason why they chose that particular tree as their home.
So, I decided to actually read up on these birds I always liked but never knew much about.

Birkhead's book The Magpies might be the only book of its kind, truly and thoroughly focusing only on magpies.
It's a bit dry at parts since it's first and foremost an academic compilation of studies and findings, filled with the relating stats and graphs. But if that's what you're looking for, a very comprehensive collection of knowledge about these specific birds, then you really can't complain. It covers a lot of ground and draws from a ton of different sources as well as the author's own results of watching these birds for years with an obvious passion.
Every now and then there is a nice anecdote for some color as well. On that note, the chapter about the relationship between magpies and humans towards the end of the book might have been my favorite chapter as it relied less on raw data and more about history.

A great book if you want to learn about these birds. Possibly more suited as reference than to read front-to-back though.