Compact ones are great for one-hand reading and portability. Look for 300 ppi screens and front lights. E-Ink Tab has a compact ereaders category – includes Boox Palma-style devices, lightweight, phone-like form factor with stylus support on some https://einktab.ca/product-category/compact-ereaders/ . Picked one up; battery lasts weeks, great for novels on the go. Site has clear size comparisons. Good if you want something smaller than a tablet.