Owning your own home

Usually, bookcases are less deep than this gap. Do you want the bookcase to be 340mm deep?

It may look better to have one that's shallower, i.e. while you'd still be able to see that the chimney breasts are different, it might be less obvious?

(You may need the extra depth to have books in there two deep, of course.)

Vitsoe. You can have a 900 + 600 wide bay and adjust the shelf depths to suit. Although 360mm is the deepest shelf they do anyway. It's not an entirely serious suggestion though, I can't think of anything better right now.

Not sure why.

Let's hope it's just because of arbitrary measuring, as opposed to something more expensive...

Do the shelves need to be rectangles, or will any old irregular quadrilateral do?

You could stud out the shallower chimney breast if you wanted them equal.

simple! add 60mm more lime plaster to the wall of chimney 1! you're welcome.

You could panel it and shim the wonky end out by 60mm behind the cladding - don't have any exact examples but could look really nice

I'd just run it at 360mm all the way across & put some bigger books on the 420 side.
If its anything like my place the alcoves won't be at right angles either so you will need to make
a card template to check.

Issue is the breasts are different depths. Not sure why.

My folks place is in the middle of the terrace and apparently they were built from the middle out. There are loads of random things like that there. For eg the doorway where the folding doors between the reception rooms is not central with either room - the placement is totally random.