This is the full retail version of CS: Source, and it also comes with the full retail version of 'Day of Defeat: Source' (it also has the standalone version of Half Life 2 Deathmatch).
UPDATE: to get the game for the price listed, look on the right-hand side of the screen for 'More Buying Choices' - there are two 'Amazon-Fulfilled' (the ones offering super-saver delivery) sellers there selling the game for around £7.70.
Current Steam (download) price is £13.99 + £5.99 = £19.98.
To show you what a bargain this is, AMAZON are selling Day of Defeat Source by itself for £11: http://www.amazon.co.uk/Day-Defeat-Source-PC-DVD/dp/B000E7Y8FC/ref=sr_1_417?ie=UTF8&s=videogames&qid=1247182102&sr=1-417
£7.69 is a complete bargain for a game that you can play for (literally) years.
This is a 'Fulfilled by Amazon' item, so all sales, despatch and returns are handled by Amazon, for more info see here http://www.amazon.co.uk/gp/help/customer/display.html?nodeId=200106510