Are you sure you don't have any Marleybone quests in your book? Sometimes I forget to look at a page, and you might be missing one. You should have the quest "Missing Souls" from Sergeant Major Talbot in the Oasis, to talk to Private Kinchley in Marleybone's Spiral Chamber. See if Major Talbot or Private Kinchley have anything for you. Sorry this doesn't help much, I just thought I would reply since no one else has.
When you get to Marleybone go straight out of the cathedral and turn right out of the square. At the end of the street talk to the castle guard. He can get you started. From there on you can just pick them up as you come to them. I like to get several in my book at a time because different people want you to kill the same "burglars". That way you can kill 4 and finish 2 quests. MB is good for leveling but you do lots of running.
If you did finish the last quest in Krok that takes you to MB, you should get a quest that allows you to enter MB. If you didnt get the quest, look at your quests icon in your spellbook OR you might of missed someone to talk to in Krok.
To get more quests from MB, look for all around MB! Hope this helped!