Aqualung was Jethro Tull's fourth Studio Album, and was recorded at the exact same time, in a different part of the same studio as Led Zeppelin 4. This said, Aqualung is not a straight forward rock album, as the previous reviewer loved to point out. What Aqualung is is a wonderful mix of inventive blues, folk, Celtic and rock music. Their are great heavy tracks, such as Aqualung, Cross Eyed Mary, Hymn 43 and in its own patient way Locomotive Breath. But, even more striking to a listener with a broad palate, are short acoustic and flute based songs such as Cheap Day Return and Wondering Aloud. Jethro Tull was a brilliant inventive band that combined incredible skill and musical knowledge with intensive rehearsal and recording to produce very tight skillful albums. Many of the songs have more than one time signature, and the shifting tempo and rich music is a refreshing contrast to most standard timing, and tuning rock music. (Zeppelin also varied timing up a lot on 4)
As for the previous reviewers claim that Jethro Tull ripped of the riff from War Pigs for Aqualung, they should note that Toni Iommi from Black Sabbath actually tried out for Jethro Tull, but was turned down for current guitarist MArtin Barre, and far from expressing any views such as those expressed by the reviewer, Iommi has stated that it was Jethro Tull that had a profound impact on his own career, and taught him the work required to be a professional musician.
One should note that Ian Anderson of Jethro Tull talks in a recent live release of Aqualung about the lead riff, which he says they wrote by rearranging the opening notes of Beethoven's Fifth Symphony, he went on to sing the notes of many other famous rock tunes and describe how they are also rearrangements of those notes.
So there it is, everyone is simply ripping off Beethoven, at least though Jethro Tull is doing it with some sense of musicianship.
(By the way, if you are buying the album for the bonus tracks, don't. They are not very good. The remastering of the album though is quite good, although not worth the purchase price if you already own it.)