Honestly, figuring out the order for 'The Land of Stories' is pretty straightforward since it's a linear series, but there are a couple of side books that can trip you up. The main six novels go in numerical order: 'The Wishing Spell', 'The Enchantress Returns', 'A Grimm Warning', 'Beyond the Kingdoms', 'An Author's Odyssey', and then 'Worlds Collide'. That's the core journey of Alex and Conner Bailey. Where people get confused is with 'A Treasury of Classics' and 'The Mother Goose Diaries'. Those are companion books—collections of fairy tales and diary entries—and you can read them whenever, though I'd slot 'The Mother Goose Diaries' in after book four or five since it fleshes out a character who becomes more prominent later.
I made the mistake of trying to read 'An Author's Odyssey' before 'Beyond the Kingdoms' once because the library had a weird shelving order, and it was a mess. Characters referenced events I hadn't read about yet, and a major villain's motivation was completely lost on me. So stick to the numbers. After you finish 'Worlds Collide', there's 'The Land of Stories: The Ultimate Book Hugger's Guide', which is a fun behind-the-scenes scrapbook, but it's pure bonus material with no new narrative. The series doesn't have prequels or a convoluted timeline, which is refreshing compared to some other fantasy sagas that require a flowchart.