What is a 'slabbed' comic book, and is it worth the extra cost?

A 'slabbed' comic book is one that has been professionally graded and encapsulated by a service like CGC or PGX. The comic is placed in a tamper-evident plastic case. While slabs provide protection and authentication, they can reduce the resale value of the comic. Whether it's worth the extra cost depends on the comic's potential value and your desire for guaranteed authentication and preservation.