This was the last album they did before the death of John Bonham, their drummer.  I remember clearly the excitement when this album came out!  Besides the great music on it there was a challenge....to collect all six sleeves in the release.  They were all covered by a brown paper so you didn't know which you were getting.  It was of a scene in a bar of a group of people watching a man burn a Dear John Letter.  Each album had a different perspective of the room.

I found this information on a website called This Day In Music:

1979, In Through the Out Door was released in the US, Led Zeppelin's last album while all four members were alive. 'Fool in the Rain' was released as a single in the US. In Through The Out Door has now been certified 6 times Platinum by the Recording Industry Association of America (RIAA) for US sales in excess of 6 million copies.

The following info is very interesting and taken from Wiki

The album artwork was designed by Hipgnosis. Storm Thorgerson recalls the design in his book Eye of the Storm:

The sepia quality was meant to evoke a non-specific past and to allow the brushstroke across the middle to be better rendered in colour and so make a contrast. This self same brushstroke was like the swish of a wiper across a wet windscreen, like a lick of fresh paint across a faded surface, a new look to an old scene, which was what Led Zeppelin told us about their album. A lick of fresh paint, as per Led Zeppelin, and the music on this album... It somehow grew in proportion and became six viewpoints of the same man in the bar, seen by the six other characters. Six different versions of the same image and six different covers.^[11]

And:

Did you ever notice you could affect the dust jacket by putting water on it? If you applied spittle to it or a bit of water, it would change colour, like a children's colouring book we based it on. But we didn't tell anybody. I don't think Zeppelin told anybody, either.^[12]

This is my favorite song on the whole album!

Here is the whole album from you tube!