Talk to Dinya Balu after The Book of Love quest and you will be able to provide her with some additional assistance. She will tell you "Riften is drowning in a sea of sin and wickedness and it's my personal mission to let everyone know that the warmth of Mara can see them through." Now, she needs a messenger to bring Mara's words to these poor souls by distributing some missives. Then, she will give you twenty The Warmth of Mara bulletins to give out to the citizens of Riften. You will need to hand out all twenty to complete the quest. Before you start the work, you may ask Dinya for some tips on who might accept the bulletins. She will tell you "Almost anyone in Riften is in dire need of those missives." However, it would be wise to keep away from Mistveil Keep and the city guards.
There are a total of thirty-seven people that will accept the missives. You can talk to them "Here, brother/sister. Blessings of Mara upon you." Although their reactions vary widely, they will always accept them.
Return to Dinya and tell her that you've given away all the missives. She will be quite pleased "Oh, splendid! Just splendid! Mara smiles upon us this day." Then, she will reward you with a random potion.
After you've delivered the 20 missives and return to Dinya Balu, you'll be presented with a dialogue option that says you've run out of missives and require more. If you select this option instead of saying you've delivered them all, Dinya will praise your diligence and give you 5 more missives, which can optionally be passed out. When you deliver each of these "extra" missives, the "Completed" quest update notification will reappear, along with the (total/20) count (i.e. 25/20 after you've delivered the last one). However, if you return to Dinya after delivering the extra missives and tell her you've delivered them all, the dialogue and reward will be identical to what you would have received had you not delivered the extra ones. While it doesn't hurt you to do this, there's no actual benefit. Furthermore, you may or may not be given the "extra" option again; some players report seeing this happen while others report that they only got the option once. It appears as though an additional reward may have been intended but was never actually implemented.
After handing over 19 missives, the option to hand over the 20th may not show. The quest is stuck at this point, and the only way to advance is through console.
The 20th missive should still be in your inventory. If you drop it then talk to Dinya, you should be able to ask for extra missives. After this you should be able to deliver the last missive and complete the quest.
Sometimes, you can give a pamphlet to someone you've already given it to. Quitting and reloading seems to trigger it fairly reliably, but that doesn't appear to be the only factor; certain combinations of saving and reloading can also cause the bug without quitting.
Reloading the same save a second time fixes the issue.
Objective 10: Distribute the Warmth of Mara within Riften (<Global=FFRiften05Served>/20)
30
Objective 20: Return to Dinya
The following empty quest stages were omitted from the table: 10, 25, 200, 250.
Notes
Any text displayed in angle brackets (e.g., <Alias=LocationHold>) is dynamically set by the Radiant Quest system, and will be filled in with the appropriate word(s) when seen in game.
Not all Journal Entries may appear in your journal; which entries appear and which entries do not depends on the manner in which the quest is done.
Stages are not always in order of progress. This is usually the case with quests that have multiple possible outcomes or quests where certain tasks may be done in any order. Some stages may therefore repeat objectives seen in other stages.
If an entry is marked as "Finishes Quest" it means the quest disappears from the Active Quest list, but you may still receive new entries for that quest.
On the PC, it is possible to use the console to advance through the quest by entering setstage FreeformRiften05 stage, where stage is the number of the stage you wish to complete. It is not possible to un-complete (i.e. go back) quest stages, but it is possible to clear all stages of the quest using resetquest FreeformRiften05.