This is the first Miss Marple Mystery published in 1930. I would recommend reading The Murder at the Vicarage first before the other stories in the Miss Marple series. The characters that were present in the village of St. Mary Mead where Miss Jane Marple lived, carried on in subsequent books.
This first book was 285 pages long and when Colonel Protheroe was murdered in the study of the Vicar’s residence, the whole village was investigated in order to catch the murderer. The investigating authority did not know at this point that Miss Marple had an analytical mind and a reputation of solving murder mysteries. Chief Constable Colonel Melchett together with Detective Slack was in charge of the investigation. They kept hitting roadblocks with statements from various people on what they saw and heard and the investigation evidences.
It was a long story with many characters and I was baffled throughout just like the investigating team. The frustrations showed. It was only at the end when Miss Marple gave an explanation of the likely events that led to the killing of Colonel Protheroe, that I know how it was carried out. It was a meticulously planned murder with a consideration of giving an alibi for the murderer.