UPDATE 9TH JUNE: There's been a bumper update to the Sale, the headline addition being Telltale's excellent adventure games. The entire Walking Dead series - Season 1, Season 2, 400 Days - is only £10.67, and The Wolf Among Us is down to £4.79. The new Game of Thrones series is half-price at £11.49.
But that's not all: the hatchet has been taken to other recent releases too. The Vanishing of Ethan Carter is £6.09, Wasteland 2 £11.99, and Shadowrun: Dragonfall £2.69. Then there's Sunless Sea for £7.49, Dreamfall Chapters (the entire season) for £13.59, and Broken Age for £6.49. Age of Empires 3 is slashed to £8.79.
There's a lot more. Best bunch of GOG sales so far.
UPDATE 4TH JUNE: There's a fresh batch of deals - and more coming at 1pm UK time - on GOG. Those that caught my eye include Legends of Grimrock 2 (Eurogamer Recommended) for £4, The Banner Saga for £3.29 (Eurogamer Recommended) and enduring classic Beyond Good & Evil for £1.70.
Grim Fandango Remastered (Eurogamer Recommended) is nearly half-price at £6, too.
ORIGINAL STORY 3RD JUNE: The GOG Summer Sale 2015 has begun. Spend $1 on anything during the sale period (3rd-21st June) and you will be rewarded with SimCity 2000 for free.
Spend $20 and you receive S.T.A.L.K.E.R.: Clear Sky for free; spend $50 and you get Xenonauts for free.
Those rewards are in addition to the expected dose of daily deals on individual titles and substantial discounts on game bundles. Apparently there will be more than 100 offers every day.
Kicking things off are a small discount (to £45) for the very new Witcher 3 - a game made in the same building GOG operates in - plus a massive discount for Witcher 2 (to £2) and for The Witcher 1 (to £1).
BioWare's somewhat forgotten martial arts adventure Jade Empire is only £2. Elsewhere, OlliOlli is down to £2, Gone Home to £3.09, and Telltale's Game of Thrones episodic series nearly halved in price to £13.79.
There are lots more deals on the GOG website.