This four-CD set purports to cover the years 1955-2001, though the 1950s entries consist of only two tracks, one seminal acoustic blues by Lonnie Donegan and the other a slightly bigger band endeavor by Chris Barber; then its off to 1961 and some raw early tracks, one studio and one live, by Blues Incorporated featuring Alexis Korner and Cyril Davies, before listeners arrive in familiar territory with the Yardbirds' version of "Baby What's Wrong." A lot of what follows across this and the other three discs will be familiar to purchasers of various Immediate Records compilations and other British blues discs that have been kicking around bargain bins -- indeed, the vast majority of sides here are from the Immediate and Pye Records libraries. The major difference here is that all of it, even the ubiquitous Immediate sides featuring John Mayall, Eric Clapton, Jimmy Page, and Jo Ann Kelly, sounds incredible -- this reviewer has worked with a lot of the material in question as a producer, and none of it ever sounded this good -- and that the producers have reached out to other catalogs. What's more, it's all been assembled not only in a sensible fashion but in an inspired way, so that it hangs together as an audio documentary of a sound and a gradually shifting era, sparked by relevant sides featuring the Kinks, the Animals, the Downliners Sect, the Pretty Things, the Primitives, the Checkmates, the Spencer Davis Group, David John & the Mood, Jimmy Powell & the Dimensions, Chris Farlowe (working under the name Little Joe Cook), Dave Kelly, Chicken Shack, the Alan Price Set, T.S. McPhee, Duster Bennett, Top Topham, Paul Jones, the Pirates, Foghat, Mick Abrahams, the Blues Band, and Gary Moore; and it's of more than academic interest -- some of those relatively little-known outfits, such as David John & the Mood on "Bring It to Jerome," are surprisingly strong on their recordings. It's all accompanied by deep and serious annotation, the 48-page booklet alone justifying 20 dollars of the cost of this set for blues fans, R&B enthusiasts, and British Invasion fans who want to hear a side of the music that wasn't as well known on this side of the Atlantic. This reviewer found the earlier sides on the first two discs to be the most interesting and exciting, but that's purely a personal judgment -- the increasing competency and virtuosity on the later sides also have their merits.