Below are a few highlights and recognized prices for Agatha Christie books sold on Ebay primarily in January. In general, Ebay is a mixed bag for collectors, often littered with misinformation, uninformed sellers and poor condition items. Occasionally real gems do show up so its often worth a periodic review of offered items. Prices shown reflect the currency used for the listing.
1943 UK First Edition: The Moving Finger in dust wrapper. Sold for £182 (UK). The book was in very good plus condition and the dust wrapper (not price clipped) was a little worse off, but still very good. Of note, the correct first edition jacket has the advert for Five Little Pigs on the rear panel - which this one did. Many books marketed as first editions have a later jacket. This book was very well bought as the true value is likely double or triple the sale price. Arguably the bargain of the month.
1945 UK First Edition: Sparkling Cyanide in dust wrapper. Sold for £125 (UK). A fairly tatty copy with a heavily repaired wrapper spine done appallingly badly. The wrapper and book are likely married as the spine of this hardback was heavily sun faded. Perhaps a fair market price, but very limited in appreciation potential given disastrous repairs and fading.
1941 US First Edition: Evil Under The Sun in dust wrapper. Sold for best offer. Was originally listed at $1,500 (US). Generally a 20% discount can be obtained from most fixed price sellers, so let's assume likely sold for $1,200. Both the book and wrapper were in above average condition, complete and lightly chipped/worn. Condition is everything in pricing and very good plus US first editions from the early 40s are starting to get quite valuable now, so I would say fairly bought and sold, and offering good appreciation potential in the years ahead.
1973 UK First Edition, signed contemporaneously: Postern of Fate in dust wrapper. Sold for $722 (US). Book and wrapper (price clipped) were in very good condition. A certification of authenticity (for what they are worth) was included. Since the book is essentially worthless without the signature, this affirms that a Christie signature from her latter years arguably adds ~$700 US to the value of a book.
1940s-50s (mostly) UK Penguin "white stripe" paperbacks - 12 in all. Sold for £100. This was a nice set with typical spine damage, wear and scuffing. A few of the more collectible ones were not included, for example The Mysterious Affair At Styles or Murder, but a few of these are fairly hard to find in very good condition, such as Peril At End House and Appointment with Death, which were both included in this grouping. A fair price for an often ignored segment of paperback collecting.