Although my own favourite Showaddywaddy albums are 1976's "Trocadero" (released earlier this year by Cherry Red) and 1977's "Red Star", which should be out before the end of the year - this is a great place to start.
Their second album from 1975, "Step Two" still had more songs written by the band themselves than the cover versions that they would become known for, during the 1977-1979 period that saw their greatest success.
Highlights include "Blue Jean Baby" and "Sing On Louise" which could both have been singles, the latter being a very nicely arranged ballad (plenty of strings and flourishes!); the catchy "If You Know What I Mean", and "Big Big Star".
The singles were a superb version of "Three Steps to Heaven", and their own "Sweet Music" - but perhaps one of the best tracks is a classic version of Sam Cooke's "Chain Gang" which gives the original more than a run for its money!!
Overall, the sound of a young and enthusiastic band (which had already managed 5 hit singles in less than 18 months since forming), but without the brass arrangements and production 'polish' that typified their sound from late 1976 onwards.
(Also worth mentioning: the Arista Singles Volume 1 which is to be released in September 2002 by Cherry Red covers 1977-1979 and includes all the A-sides and B-sides from their most successful period...it's a must have!)