In order to receive this mission, you have to speak with the wife of Adril Arano - Cindiri Arano. She can be found at The Retching Netch or at the streets of Raven Rock. She will tell you that the ship carrying her book has sunk nearby the shore. If you manage to retrieve the precious volume - the Lusty Argonian Maid Folio - you will be handsomely rewarded.
The wreck can be found at the southern shore of the island, nearby Old Attius Farm. Bandits have made camp around it - in order to get inside and retrieve the precious book, you will have to defeat them. Don't worry - they aren't very strong, so fighting your way through them shouldn't be a problem.
Once onboard the ship, head below deck and search for the treasure chest with the Lusty Argonian Maid Folio. Look around the area to find an East Empire chest - its content will come in handy during Locate the East Empire Pendants for Fethis Alor in Raven Rock.
Return the Folio to Cindiri Arano in Raven Rock
Return to Raven Rock and give Cindiri Arano her book back. She will in return give you a magical item, the quality of which depends on your level. Despite that what you did for the woman might seem like not a great achievement, indeed the whole coast will be glad that you took care of the group of dangerous bandits. Apparently small acts can sometimes develop into great deeds - you just need some good will.