Approx. 5/8" wide x 7/8" tall x 1/8" thick (aka: 15mm wide x 22mm tall x 3mm thick). See below for collage sheets sized to fit these books (plus the one shown in the main photo above is Tiny Magic Books & Potion Labels).
Set of 4.
One of these is also included in the Apothecary Bottles Kit; see all the other kit components available to buy separately.190926SC 180812SC 211111CL tiny little small 150405KTT 150416SVV 220717CL 150709tbs 150723sbk 150806slb 150830DLO 151022TWR 151025FTB 160515LCS 160616SC 112cabbtls 160821AC 160901RS tnybooks 160908BT 160908NB 190915LM 161126NB 161125RT 170209RT 170518GK 170524LM 170622SC 170712RT 170921RT 171217NB 200712KB 200719SC 210912new 220828SC 221002octPBKt 221020RT 210114SC