Trout Mask Replica is a little bit of a rough fit the first few listens, definitely, it's terribly dense as a complete musical piece, in particular with so much going on in every arrangement and the rhythms being all over the place. It's a top-to-bottom masterpiece though. If you want an easier start try Safe As Milk, it's much more standard 60's blues rock, but of course with Beefheart's unique pastiches of surreal musical insanity slathered all over it. If you want to stick with his more avant-garde material, the best ones other than Trout Mask Replica are Lick My Decals Off Baby, Doc At The Radar Station, Shiny Beast (Bat Chain Puller), and Ice Cream For Crow.