What is the little blue book icon to the right of my health bar when I sit down?

[Professor Von-Wulfen ]

As above :)

[Amroth]

That means you get a bonus to reading while sitting.
The bonus will be even higher in bed.

[Corvey]

It's a buff for reading. Certain locations give you this buff and while it's active every book you read gives more experience towards your reading skill as well as you read it faster than normal.

[Barc_7]

u can see all explanation off your active buffs if u press "p" and go for "buff"

[Professor Von-Wulfen ]

Many thanks all.