Sometimes, a book just sort of flows. Whether you plan first, or you are a pantser, it is all clear from the beginning and when you get to the end, there's very little you need to adjust.
These books are a delight.
Sometimes, a book needs to be dragged out, kicking and screaming. When you plan first or are a panster, you can see it's outline but the matter of it just won't come and every word seems to be hard. But it comes, slowly but it comes, and when you get to the end you often have to do some re-writing of the beginning to make it match the realisation you came to at the end, but it's done in a couple of drafts.
These books are a challenge.
Then there are the books that it seems will never be write. You do the first two drafts, and it's kinda there but not quite. So you put it aside for a while until you can see the problem. You fix it, but it's still not right. Then you realise the entire premise is wrong, so you go back and re-write massive bits of it. And now the premise is kinda working, but the whole thing isn't knitting together. So you put it aside for a while until you can see the problem. And you find it, and unravel parts and re-knit it all together and now it is singing, and then it stops singing and buggered if you can work out the problem now, so you put it aside again. Then, somewhere around the tenth draft, you finally work out what you were trying to do in the first place, and you re-write bits and you write new bits and you pull it apart and you put it back together and finally, finally, you get it.
These books are the shits.
But they are also the books you learn the most from. The books where you have tried things, and failed, and then you work out why they failed and then you become a better writer. Something like one in every six books does this to me. The one that is hammering my arse at the moment is the second book in the gadda trilogy. The main problem with this one was that it actually didn't have a purpose beyond getting a couple of people together because I hadn't worked out the antagonist's plot and what this meant.
So now I'm trying to fix it to show it's rightful place in the trilogy. It will work, and it will be good, and I am grateful for the strength it has created for the entire trilogy by being such a pain in the arse - but I'm on draft nine, and I've been trying to get this thing right since 2011 and it is really, really shitting me.
Sometimes writing is great fun. Sometimes it is a pain in the arse.