I'm not generally a fan of marketing because I've found most of it doesn't work well enough to justify the time. I have found one exception for certain types of books in Amazon. Marketing on YouTube takes effort, but the videos do not have to be professional to be effective. This book gives a process for marketing that may work for you.
This is the video series that has worked the best for me: https://www.youtube.com/user/bnaiorpueblo
Types of Books
Marketing on YouTube may work for non-fiction books where a long series of videos can be published. YouTube's search engine favor titles like "Lesson 1...etc." It seems to be completely useless for fiction.
I don't want to over-hype this. If you aren't getting viewers after five or six videos, it may not work for your book.
I have one video series that gets about 400 views a day and refers about six clicks a day to my book "Simply Learn Hebrew." This doesn't sound like much, but I haven't added any new videos in over a year. YouTube videos don't seem to have the same decay rate as blogs if they are neglected.
Give away the whole Book
I found it's best to include everything in the book in the YouTube videos. Only the first few videos in the series will get many views. The first few books give the most clicks to the books.
Keep it Simple
It shouldn't take more than an hour from start to publish to make a video. If it takes too much longer than that, it may not be worth the time.
YouTube videos seem to be the most effective form of marketing. Short videos are easy to make if they are not production quality. They have a slow decay rate for the number of views, so they can keep selling books for years with no attention. They are worth trying.
One of the most effective means to advertise a book about a long hike on YouTube is to give a one or two minute summary at the end of each day. For the 48 state hike, that would be about 300 videos which are certain to attract attention and sell books.