More specifically, left click an drag the mouse cursor over the text (or right click the page and click 'Select All').
For the plague quest;
talk to Huge, in the farmhouse just north west of the castle.
visit the quarantine area and see a cut scene with the doctor (the guards will not let you enter)
enter the cave just south of the farmlands...
Spoiler ~~[color:"#27384A"]... and get a key there
check out the basement of the Blue Boar inn
talk to the bartender about what you find
enter the doctor's house in Ars Magicana and talk to the him, you will get kicked out
get the key just south east of his house and re-enter
explore ... notice anything 'strange' about the lanterns?
find evidence against the doctor, as well as two cure potions
leave; the doctor meet you in the front room
report to Lt Robin, IIRC then go talk to Commander Ralph
return to the poor quarter; Lain (IIRC, the guy who directed you to the thieves' guild) has a key to the back door of a house straddling the quarantine fence, or you can use Lockpick
talk to the three people there and cure two of them
either kill one of the cured people or use Pickpocket (level 2) to get a cure potion back for the third person[/color]~~ (highlight the text to read)
more details:
Plague Problem & Harvest Diseaster