Learning about the Leech Lattice I am a college freshmen currently enrolled in a second semester of abstract algebra and a course on error correcting codes. I've read about the Leech Lattice online, and I'd be very interested in learning about it and its connection to sporadic groups and Golay code. Are there any books/resources about it that I would be able to understand, and if not, are there any prerequisites I should learn first? Thanks!

start with Thompson's book. Then Ebeling on lattices, which helped me a good deal. Let me look up full titles

Thomas M. Thompson, _From Error Correcting Codes through Sphere Packings to Simple Groups_

Wolfgang Ebeling, _Lattices and Codes_ there is now a third edition

Well, why not. A technique that was probably invented by Conway shows that any "even" lattice with covering radius strictly below $\sqrt 2$ has class number one. G. Nebe first published a list of these, maximum dimension possible is ten (goes back to G. L. Watson). I and Pete Clark published a small correction by finding lattices with class number one. Meanwhile, the Leech lattice has covering radius exactly $\sqrt 2,$ and class number $24.$ The thing about the covering radius is that one may draw pictures for the two dimensional case, on ordinary graph paper, and learn a good deal.