I am trying to gain a better grasp of how to build an AM radio receiver. Can you direct me to some books (or other information) that will help?
A great textbook for building a receiver or transmitter from scratch is Solid State Design for the Radio Amateur, by Wes Hayward W7ZOI and Doug DeMaw W1FB, published by the American Radio Relay League in 1986. (If you were hoping to build a receiver that uses tubes, then this book would only be indirectly useful.) Unfortunately it's been out of print for many years, and ridiculous prices are asked for used copies.
However, it can be found on archive.org here. Thanks to the ARRL for apparently allowing the book to be read online! What's more, the ARRL also seem to have shared several editions of the Radio Amateur's Handbook / the ARRL Handbook, which are also excellent resources.
If you want to learn how a radio works one good source of information is Bob Heil's pine board radio project. It is a tube type radio, but even if you don't build it you will learn a lot about radio.
Most HAM HF radios are SSB or CW instead of FM, but there are many books on all types of radios. On Amazon do a search for books published by the ARRL or if a ARRL member you can purchase them for the website.
ARRL also publishes a magazine, QSX, for radio experimenters. At the moment it is a separate subscription, but they plan to offer a digital subscription to all ARRL members in near future.
I have a copy of The ARRL Handbook for Radio Communications from 2014 but they make a copy every year. The 2014 copy i have is one large hard cover book but they also make it in soft cover. The last few editions have been broken down in to a set of 6 soft cover books. It is a bit pricey but it is available used for fairly cheap(around $5 for copies from the early 2000's) online. If you have a good local library they may have an electronic copy you can "check out."
I found this copy of the 2019 edition online: http://web.archive.org/web/20200407064826/https://3v8hb.files.wordpress.com/2019/04/the-arrl-handbook-for-radio-communication-2019-v2.pdf