There are several POD publishers but Createspace is part of Amazon, a distinct advantage as you can imagine. It lets you set up the whole process yourself if you've got the time and inclination, but even using a professional, the process is relatively inexpensive. Get in touch for a quotation. If you want to get to grips with what is involved, here is a link to a PDF created by Amazon that gives full DIY instructions.
If you have created your book interior, this calculator will tell you how thick your spine should be depending on paper type and number of pages. Note that books with less than 102 pages are not thick enough for a spine. Createspace suggests 130 pages is safer. this can usually be easy to achieve with a largish font size, large margins and a few empty pages.
My name is John Amy, I am a professional graphic designer based in the UK with over 25 years' experience, and design print books as well as ebooks. Just email firstname.lastname@example.org with an outline of your requirements for a no-obligation quote or call me on 020 8462 0969 or 07773 218 349. If you have any questions or problems about design and branding or how to go about getting a professional-looking ebook, please get in touch. If you are outside the UK, don't worry. My clients span the globe. The beauty of the digital world is that it has a global reach. My graphic design website: www.promo-design.co.uk.