Whether it’s Clark Ashton Smith to George Sterling, or David Lindsay to E H Visiak, reading letters between writers, you often find things getting a little formulaic. So, if you ever get caught in a writerly correspondence (highly unlikely, nowadays), here are all your epistolary requirements met:
Dear [fellow writer]
First of all, apologies for not having replied to your previous letter sooner. You know how life is!
[Then, either this paragraph:]
Thanks for the copy of your latest book. A work of genius, though few of course will see it. Critics are, in the main, dullards. As for me, it has left my head so full of thoughts that I cannot set them down just yet. A second read, and a bit more leisure, will allow me to do so. Now, of course, you must immediately set about writing something new! The world awaits your next masterpiece!
[or this paragraph:]
Commiserations on your continued efforts to find a publisher. Publishers are, in the main, dullards. It will, I am sure, one day soon find a home.
As for my own writing, I have been rather lax of late. All this business with moving house, and so on. You know how life is! I will endeavour to do more!
[your name, in a slightly less formal version than in the last letter, till you hit on a pair of silly nicknames for one another]