Queen II was recorded at Trident Studios in August 1973, chiefly produced by Roy Baker, chiefly engineered by Mike Stone (Father to Son and Seven Seas of Rhye being notable exceptions) and released on 8th March 1974. Freddie Mercury was the album's chief composer, lyricist and arranger. It was a moderate commercial success and their first release ever to be No 1 somewhere (Belgium, to be precise). The album was massively popular amongst fans, band members, crew and other musicians.
While not by any means a concept record, it's arranged by 'blocks' of tracks by the same songwriter, a concept which is similar to (and possibly inspired by) Pink Floyd's Ummagumma. In fact there's a lot of Pink Floyd on this record: compare Processionwith Speak to Me, basically the same intro. It's worth mentioning that, by the time Queen II was being recorded, Dark Side of the Moon was a huge commercial success in Britain. Pink Floyd were one of the few bands all Queen members seemed to be quite fond of; Deacon, May and Taylor mentioned them in interviews over the years, and Mercury's driver/PA confirmed they were one of the groups he used to listen while being chauffered.
Film sequels tend to expand on character development, take whatever worked (either commercially or aesthetically) the first time and boost it, and explore different angles. A similar phenomenon occurs when it comes to musician's sophomore efforts. This one features more variety and each band member covered more functions and roles: Mercury played harpsichord and jangle piano in addition to grand (which, by the way, was brought to the foreground much more than on the previous LP), May sang lead vocal on a track for the first time and also played some percussion, Taylor not only sang lead vocals on his own track but all the harmonies as well, Deacon played acoustic guitar in addition to bass; moreover, the author of each particular track assisted either Roy Baker or Robin Cable (or both) as second producer.
The album's liner notes claim that 'nobody played synthesizers ... again', which is technically not true since there are ca. 10 seconds of stylophone (played by producer Roy Baker) at the very end of the record. They sort of got away with that and, though the matter wasn't addressed directly in an official way, it could be quibbled that they probably meant nobody played five-plus-octave keyboard synthesisers (such as a Moog or an EMS).
It tends to be claimed (on magazines, books and the web) that Queen were now considered a VIP client for the record company and that's why they had full use of the studios instead of recording downtime as they'd done for the first album. Well... yes and no; truth is, Trident Studios weren't nearly as popular as they'd been the previous year, and their biggest clients were, in a domino effect, choosing other recording venues: Mott the Hoople at AIR and EMI, Harry Nilsson at Apple, Genesis at Island, and others had left the country: Paul McCartney did most of his album in Nigeria, David Bowie in France, George Harrison chiefly in America; Elton John did record part of Brick Road at Trident, but that was earlier in the year, and by August he'd long vacated the studios. So it was more a matter of the actual VIP's being elsewhere and the studios magically being available full-time for those who were lower in the pecking order (let's face it, in August 1973, Queen were still 'commoners', who'd failed to chart and who were lucky to be paid to make a second album at all).