The last instalment of the series, in which a modern day twenty-something is thrown into the 'real' fictional world of the novel through an opening in the bathroom of her Hammersmith flat, captured a 13.5% share of the audience between 9pm-10pm.
The viewing figures are up on last week's 2.9m viewers, but down on the opening episode which brought ITV1 3.8m viewers. The second part drew 3.1m viewers.
The prime time slot was won by the penultimate instalment of BBC One's 'Who Do You Think You Are?', in which former model Jodie Kidd traced her family roots all the way back to the 1620s.
The seventh episode of the series had 6.2m viewers and a 27.7% share in the 9pm-10pm slot.
Channel 4's experimental documentary 'The Family', in which an ordinary Kent family are the subject of a fly-on-wall series across eight episodes, attracted 2.2m viewers and a 9.9% share for the second episode. Including viewers on Channel 4+1, it had 2.5m viewers and an 11% share. Its debut last week was watched by 2.7m, giving it an 11.5% share.
'Britain's Youngest Grannies', a documentary about grandmothers in their thirties, brought BBC Two 1.4m viewers and a 6.1% share between 9pm-10pm.
The Jean-Claude Van Damme action thriller, 'Second in Command', earned Five 1.3m viewers and a 6.5% share at 9pm-10.55pm.
On the multi-channel platform, the first episode of ITV2's 'Jack Osbourne: Celebrity Adrenaline Junkie', in which Osbourne and famous friends such as Hollywood actor Elijah Wood tackle extreme sports, debuted with a solid 424,000 viewers.
The show, which has been heavily promoted with on-air trails across ITV's channels, took a 1.8% share of the multi-channel audience.