I could be mistaken, but I consider my current work-in-progress, my first book, the hardest. So by association, I would say the first book is the hardest for most authors, especially if you are strict on yourself and want to make as little beginner mistakes as possible. If you are in love with your story and must make it the best. Once I heard from a famous writer that you probably should start off with a smaller, not so important project and move on later to the stories you are dying to write. I didn’t follow that advice and neither could I, because I usually am passionate about most of my stories, but I still consider that advice wise, even if it’s meant for less impulsive people than me.
On your first book, you have a humongous learning curve. There are so many ways you can improve your writing that I couldn’t make a list of all of them, let alone which one I would consider more important. I could make a list of the books I already looked in topics like Structure, Characters, Viewpoint, Description, and Setting, but apart from books, there are tons of resources on the internet, amazing blogs on writing, videos, podcasts, online courses and so on.
Books are my favorite source of information though because on the internet you often jump from an interesting blog post on writing to facebook and then all your concentration gets lost. And a book will cover a subject in many more pages, in a longer way than any blog post can. And in a book I can underline the most important tips and read them again, I find that easier than jumping back on a video. Again, each one has their own way to learn. For me the less distraction on the side the better.
Together with learning the craft you have to find your own writing system. Once you establish what works for you writing tends to get easier. I wrote my first draft as fast as I could and then I had to establish a certain order to my rewriting process and this proved to be quite time-consuming. There were too many aspects to revise and it looked the first time as too much to juggle. Later I saw I should make a reread for each of the aspects I wanted to improve. It seems like a simple idea, but it took out the overwhelming side of revising out of the way. Now I just need undisturbed revising time to use all the insights I gained so far.
So, was your first book the most difficult? What lessons have you learned with it?