I was reading this Novel for second time. Even though i knew who the murderer was, i was not able to unravel the mystery till the narrator's last explanation (it might be because i did not deploy my little "gray cells" with method and order, or Agatha Christie knows the best way to present a story).
In the town of King's Abbott what will intrigue you the most was reluctance of Dr. Sheppard to involve "Ecule Poirot" (i think "Ecule Poirot" is more cool than "Hercule Poirot" ) in investigating the Murder of Roger Ackroyed. Poirot was right when he committed that he should have the "whole truth, however dirty it may be". This mystery is more adventurous as every minute is accounted for in the crime committed.
If you try and plot the events with respect to time (this may not make sense to all of you), you will find the variations.
Either it is the events in summer-house or it is the relationship of Captain Paton with young and handsome girls, things changed in very short span of time and they had very decisive effect.
It is the story of a happy town, cheerful sister, mysterious neighbor and a ______ brother ( Well, read the story and you can choose the right adjective for The Brother )
...PAPA POIROT signing off