Editors at book publishing companies when receiving submissions for non-fiction rarely read the full manuscript - even if it is sent to them. I know that as an Agent and it is why the emphasis should be on a "killer" book proposal supported by a couple of chapters from the manuscript. Frankly most of them don't have the luxury of time to read the full manuscript - at least initially- but what they do need is the sort of information that goes into a well-prepared Proposal. Some of the key ingredients of the Proposal are the-
-Book Outline or Description - key to helping the editor quickly understand what the manuscript is all about and if done well is used to share with other people at the publishing company.
-Your credentials. - for most non-ficiton subjects the authors level of authority to write about the subject is based on things like their career background within the subject they are writing about; their education as a fit to either write or be knowledgeable enough about the subject; what special skills they might have such as doing public speaking; their website; being on facebook or You-Tube, linkedin and so on. You may not be involved with all of these examples but the more you are the better interest there will be in you...and your manuscript.
-Your writing ability - it is expensive for publishers to see their editors having to spend more time than they should on a manuscript that is not well-written. The sample chapter(s) are meant to indicate the answer to that sort of concern. That is why it is a good investment to have an experienced book editor at least review and edit as needed the sample chapters before being submitted.
There are other ingredients to completing a Proposal and I can't do enough to encourage your attention to being sure it is complete and informational. If all goes well it becomes an important marketing tool in dealing with editors at book publishing companies...and getting that elusive book deal.