For long-form, book-length work, I find Scrivener to be ideal as an environment to gather all the string. The UX and interface allows you to keep material organized in a clean and sensible way. Even simple things like their word count/tracker system encourage you to get the work done. It is far better than Microsoft Word for long-form projects, and I recommend it with enthusiasm.
This is far and away the most efficient, quickest, and most cost-effective transcription service out there. The team at Otter.AI also does an exceptional job of updating the product design regularly, and their small tweaks make a big difference. The mobile and desktop versions operate well with one another, and for interview-heavy projects, this software is a dream.