For Swedish uniforms (and also its enemies) you have the very detailed books by Lars-Eric Höglund. They are available oon this site:
http://www.acedia.se/engbok.htm
A good overview of the Great Northern War can be found in Robert Frost's book "The Northern Wars - 1558-1721" (published 2000). It cover a much longer time period than just the GNW, but it is definitely an advantage to get the full background story and learn how Sweden with its limited resources managed to become a great power in the first place and thus how difficult it was to defend that position in the GNW.
The principal character of the GNW was the Swedish king Charles XII and the best biography of him in any language is Ragnhild Marie Hatton's book "Charles XII of Sweden" (published 1968). Her strenght is however not so much in military history but in her understanding of the diplomatic side of the war (as well as having a neutral point of view and not participating in the long running trench warfare over whether Charles XII was great or terrible as king, which characterise Swedish books about the subject).
