I disagree. I think Christie is one mystery author who rarely cheats by withholding clues. It’s all there on the page. It may be subtle and require great deductions, but you can do it. I estimate my own success rate at around 50/50 or slightly higher. The ones I miss I can almost always remember back and kick myself for missing it.

Arthur Conan Doyle, on the other hand, withheld information from basically all of his Sherlock Holmes stories. There’s a reason he titled so many of them “The Adventure of…” You’re supposed to marvel at Holmes, not solve a mystery.