This is a key question that I find myself pondering as I work on the order of poems in the mansucript for my first full collection. Do we read from cover to cover or do we dip in where the book just happens to open?
Well, my own feeling is that people read in both ways. As for myself, I tend to move through a collection from start to finish on a first reading. This is to try to get a grip on how it ebbs and flows. Afterwards, however, I'll return to the book at random, flicking back and forth, digging more deeply into individual pieces.
As a consequence, I'm breaking my poems down into pairs that engage in dialogues with each other, all within the framework of how I want the collection to read as a whole. Furthermore, I'm continually bearing in mind Matt Merritt's remarks to me in a conversation a few years ago: as a journalist in his day job, he felt we often read poetry books much as we read newspapers, in that the right-hand page attracts more of our attention.
After every revision I print up and provisionally bind the collection, ensuring that the left-hand, right-hand ordering is respected throughout. I then go back over it, viewing it as a whole, viewing it in pairs. All those revisions will click into place one day, just like when I chip away at an individual poem, and I'll suddenly know the manuscript is ready!