Reddit reviews New England Getting Started Garden Guide: Grow the Best Flowers, Shrubs, Trees, Vines & Groundcovers - Connecticut, Maine, Massachusetts, New Hampshire, Rhode Island, Vermont (Garden Guides)

Most books are either about growing ornamentals or vegetables, not both, so it’s hard to make a recommendation without narrowing down your interests. Indoor gardening is a whole separate category, and I don’t doubt that there are plenty of books devoted solely to succulents, although I’m not personally familiar with them. You could try asking the folks at r/succulents for some suggestions.

Anyway, I wouldn’t say that there is any one “must-read” gardening book. I happen to like New England Getting Started Garden Guide as a basic reference for ornamental gardening. For vegetable gardening, I have an old hand-me-down book from my mother that is almost certainly out of print, but this one looks like a good starting point. You could also check your local library—they probably have some good basic references.