This album is really a mixture of two styles: the Progressive arrangements done with Classical Music influences, and Rock music tending more to Pop music, which IMO, it is a very interesting mixture. So, this album is more balanced between the styles in which ELO`s music was created. Their next album, "Face the Music", is more oriented to Pop.
This album has very good orchestral arrangements, like influenced by Classical Music composers. Orchestral Conductor Louis Clark had his first appearance on an ELO`s album, and the arrangements wee done by Clark with Jeff Lynne and keyboard player Richard Tandy. These orchestral arrangements (and choir arrangements too) were going to appear regularly in later albums, but later albums were increasingly more oriented to POP music and Disco Music. Anyway, the quality of ELO`s music is very good, even in the context of music designed for the Hit Parade.
IMO, the most interesting songs in this album are "Eldorado Overture", with great orchestral arrangements. "Can`t Get it Out of my Head" is one of my favourite of ELO`s songs. "Boy Blue" has again a very good orchestral arrangement, sounding for me like influenced by one of J.S. Bach`s "Brandenburg Concertos". "Laredo Tornado" is one of the best, a rocker song, with some use of lyircs written in Spanish: "Adiós amigos". "Mister Kingdom" also has the use of contrabasses playing low notes, a remembrance of their first album, maybe. In this song, again, the Classical Music arrangement theme used in "Boy Blue" appears again.
The rest of the songs are good too, but are more "conventional". One funny thing for me is the orchestral and choral arrangement used in the end of the "Eldorado" title track: it sounds to me like influenced by the background music used by Hollywood films done in the 40s!
In conclusion, this album has very good arrangements and a balance between their Progressive and Pop/Rock tendencies. Their later albums are increasingly more Pop influenced, but ELO`s music is very good. Jeff Lynne is a very good lead singer and composer, not matter if his music became more commercial with the passing of time.