Some never publish books. Some never submit to magazines. Magazines can be trailers for books.
I seem to have 3 routes for sending out poetry to the world: Magazines, Chapbooks and Books.
In theory poems are gathered and sent to magazines. Those that land successfully are gathered into chapbooks. Chapbooks that land well are collated into books.
However I mostly send different poems to magazines than chapbooks than books, without a lot of overlap. Partly because magazines want a theme, and chapbooks are that unit of thought long. I still have chapbooks left so don’t want to undercut sales by putting them in books and I want to give people new poems in books.