Both publishing houses and self-publishers have a vested interest in controlling the costs of book production. Although artwork -- and by that I mean photos, illustrations, line drawings, charts, and graphs -- adds to the value of a book, it also can add significant time and cost. Why is that? Here are the biggest drivers:
What good timing you have! For my book, I went through Lightning Source because the quality is said to be better, you can set your discount rates (good if you want to be in bookstores), and I am not a fan of Amazon as a company.
Things did not go as smoothly at LS as I had expected. It took three proofs before we were satisfied that the print quality was going to be all right. We have some shaded boxes, and the shading was uneven. Apparently our proof was the last book off the press before they changed the ink (seriously). I was not impressed. The cover and paper were very good though.
Over Christmas we learned that Amazon was taking longer and longer to get our books to customers. Cathy Davis reported having to wait 3 weeks! Then they started saying our book was out of stock. We finally decided it was in our best interest to work with CreateSpace and LS at the same time. I wasn't thrilled with that because, if LS has print quality issues, what is CS going to do? Most people order from Amazon and therefore the books would be coming from CS. And I don't want my readers getting crummy-looking books. But, I was over a barrel, so I signed up for CS.
Turns out the print quality at CS was better than at LS and we had nothing to worry about there. It is clear to someone who is really looking closely that the binding is not as good, and the color match on the cover isn't exact, but only we would notice that. The paper is a little creamier than I would have wanted, but I prefer it to the stark white that is the other option from CS. LS's paper is a very pleasant light cream; CS's is a little darker but still OK. Also, CS charges less per book, by about 50 cents. When you're ordering 150 books for various events, that makes a difference.
Right now we plan to keep both accounts -- one with LS and the other with CS -- but I do wish I hadn't waited so long to sign up with CS. I hate that Amazon controls everything, but with the quality of printing I saw and the cheaper per unit price, I came to terms with it.
Given the type of book you are creating, I would definitely consider using CreateSpace. You can sign up for free and get a proof for about $4 (plus shipping). If you hate it, you can move on to Ingram. Or you can sign up with both. If you do go with CS, consider getting a matte finish on your book. I find the glossy from CS to be too shiny. The matte we received looks really good. Since you have a self-help/spiritual book, I think the matte would suit your genre.
So, there's a long answer to a short question. I hope it helps!