As I been following the Beatles nearly for thirty five years I always wondered if the album was unplanned

Found the register you record part and details, it was when I went to register them, you need to sign on, that’s the bit I could not find, probably staring me in the face.

There's a small 'Login' tab above the 'Register Your Copy' bit.

Sorted, now what's the difference between 'Thin and Thick Spine' apart from me being a bit thick.

Difficult to say without having one of each to compare I guess.

Probably was! I'd only ever seen it in second-hand shops and it looked a very sloppy presentation, especially in the way the song titles were grouped on the rear cover with no real effort to list them by track number or group them into Side A, B, C or D listings. It's probably why I never bothered buying it.

The thick ones are obviously thicker often referred to wide spines on other sites. They are wider than the closed album sleeve and often looked pinched in. Have a look at the images on this ebay listing they show it quite well

Not sure what you mean by unplanned. Obviously, they knew they were making it! So far as the artwork goes, they had a fantastic cover painting done for the album, provisionally titled A Doll's House, until the Group Family released their own Music In A Doll's House, forcing a change.

Several new cover designs were submitted including one of the Beatles' heads carved in rock - in the end artist Richard Hamilton won out, with the plain white. McCartney wanted there to be a blemish on it, and suggested a droplet of apple juice. It was also his idea to put numbers on them, like limited edition artworks.

So, all in all, I think the planning was there. Whether you like the result or not is another matter. I preferred the original painting, which was eventually used anyway, here, as I think it much better suits the mood of the music.

Got you. I always put it down to minimalism.