The founding text is Snow Crash by Neal Stephenson (1992). It's short, funny, entertaining, and full of new ideas in a freewheeling early 90's spirit. The list in the comment you are replying to is not bad, since most interactions you will ever have with someone about a metaverse will hinge on shared descriptions you have with them of a metaverse, so whichever books you hear about the most are by definition the most useful ones to read.

Almost everyone has read or heard of Ready Player One (2011), which contains extensive descriptions of its own corporate dystopic metaverse, albeit one that I find insufferably cliche and unoriginal.

Metaverse descriptions are descended from the first cyberspace descriptions in Neuromancer (1984) which is a beautiful book worth a read.