From handing in final artwork, it takes about six months before I have a book in my hands. When it comes back in book form, it looks very different compared to seeing print-outs or on screen and you get a kind of 'surprise' to hold it in your hands. If all has gone well (with print) then it's a good feeling.
For me, the biggest challenge was keeping it simple and making the story engaging. My timings on this project were also pretty tricky as I was working on another project at the same time, and found it difficult to make the book's original deadline in 2017. If I could do anything differently, it would be to manage my time better and be more realistic about how much work I'm able to produce. But in the end, my editor was really good about making sure I was happy with the work before handing it in for print.
I'm happy with the final outcome of the book, and I think my publisher is too. However it's a book not a personal project, and it has to sell copies for it to be considered a success, so to a certain extent, I will have to asses how well it does based on sales.