Here is a great article on why poetry chapbooks are so important: by Michael Young, published on THEthe Poetry.
All publishing poets know what chapbooks are. So, I’m not going to provide a history of the chapbook. The internet is full of good essays documenting that history. In fact, one brief essay can be found here on TheThe Poetry Blog by Sam Riedel. Here’s another link to one by the British historian, Ruth Richardson. What I want to draw attention to is the importance of the poetry chapbook and the folly of considering it as less significant than a full-length collection. Read More
the poet's billow 
I put one of these together with my poetry and give them to family and friends. Just didn’t know they were called chapbooks. :) Now I know!
Thank you for such a fortuitous post! I am prepping a chapbook for a contest, and this is an excellent resource!
An intriguing article. It is one of those things that once one sees the argument it becomes laughable that it actually a problem — a book of poetry under 48 pages is not to be taken as seriously as those of 48 or more pages. As if a painting had to be at least 8×11 to be considered an acceptable painting to be hung in a gallery.
That many poets buy into the notion it is not surprising, being human themselves poets are not immune to the “conventional wisdom” of marketing departments and others who determine what will be and what will not be published. Yet Michael Young puts it well:
“A poet should write and construct the best book they can, and if that collection is under 48 pages, then that is how long it’s supposed to be. To ignore a collection because it’s only 20 or 30 pages long rather than 60 or 80 pages is simply the error of a mind that thinks bigger is better.”