Anybody here familiar with Yvert & Tellier?

I would suggest Y&T reflects its European and French origins. Thus, the coverage for Europe is more detailed than for the rest of the world and the coverage for France and former French colonies is more detailed than for other countries.

I should think that, from the four world wide catalogs, Michel has the most detailed coverage by far in terms of varieties and stamp issuing entities. I rank Scott and Y&T on second place finding them somewhat comparable. SG Stamps of the World ranks last - it is indeed a very simplified catalog. For how the catalogs compare in terms of listed stamp issuing entities, I have the following numbers: 




When you are looking for additional information to the Scott catalog I would most certainly recommend the Michel catalog - Y&T will, I guess, not have enough additional value to justify the investment.

You may be familiar with this but what should help English speakers get on their way using the Michel is the following booklet: An introduction for English-speaking readers