Peter Mayle is one of my favourite writers, who resurrected the art of travel books - he is one of the few still able to write with an easiness, wit and refined taste of French courtesan of XVII century.
The only one who has more depth and knowledge (although less eager to please) is Bill Bryson. Anyway, Peter Mayle almost single-handed through his talent destoyed Provence (in a similar way years ago Corfu was devastated by the books of Gerald Durrell).
I really enjoyed the book, which is easy and pleasant to reed - as usual. There is no need to argue about some expensive habits which are not even mentioned there (how about Sotheby's and collecting).
But: I do really beg your pardon, but when it comes to caviar, Mr Mayle knows almost next to nothing - as well as the majority of "grands restaurateurs", chefs, authors of books on Russian cuisine, etc, etc. By the way, Wikipedia does slightly better.
In any case, caviar perhaps is the most expensive product (1 kg might fetch between $ 5.000- 10.000 approximately - depending on the greed of the seller, stupidity of the buyer, and, of course, quality). However, it is strongly recommended to try it - at least, you'll discover what the real haute cuisine is (was), and why it was so praised by the great gourmets of the past.
So, strictly speaking, caviar ("ikra" in Russian) comes from sturgeon ("osiotr" in Russian) fishes: beluga (Huso huso), sturgeon (Acipenser), sterlet (Acipenser ruthenus) and sevriuga=starlet sturgeon (Acipenser stellatus). Beluga is (was) the biggest sturgeon with the largest-size caviar, while sterlet - the smallest (with the smallest caviar). Sterlet in the past was served was the Tsars especially, and was famous for particular Tsar's fish soup ("ukha" or "oukha"). Smoked sevriuga has an oustanding taste also. All sturgeon fishes belong to vanishing species ( and caviar too) due to pollution, overpopulation, mass destruction of habitats, etc, etc.
The main suppliers of caviar are (were) Iran, Azerbaijan, Russia, and this black gold came mainly from the Caspian Sea. Let's say, that it is considered as "apellation controlee", and true caviar comes only from that area.
So, in brief, caviar is the roe (eggs) of sturgeons, processed and salted. The following grades (standards) exist(ed) since the end of XVII century:
(a) Depending on the species of the fish: beluga, osiotr ("osetrovaya"), sterlet and sevriuga;
(b) commercially, granular (or "zernistaya") - cleaned (sieved) through special sifter, and consising of separate eggs, is considered as the best(see below). The top grades (I am afraid, not existing=available anymore) were: "troishnaya" (fresh roe was not salted, but treated with the brine, then dried naturally, packed hermetically in wooden barrels and delivered on "troikas", thus the name); then "steamy fresh"; and, finally, famous "malossol" (means little salt);
(c) also less attractive (than granular) for the ignorant, and almost not available in the international market, "payus" (or "payusnaya") should come first - this is top-grade pressed (or crashed) caviar, which looks a bit like solid black butter (and top quality can be spread with the knife). The highest possible quality of payusnaya caviar was Kuchugur, or Achuyev - known for its slighly earthen flavour. It is agreed between true connoisseurs that payusnaya caviar is well above malossol;
(d) So-called "bags' caviar" ("meshochnaya") - granular caviar dried in the open and packed in linen bags - most probably, doesn't exist anymore
(e) Finally comes the lowest grade - "yastyk" or "yastychnaya" - pressed or crashed and uncleaned properly. That was caviar "for the poor" (in the past).
Caviar should never be served frozen. Only a totally ignorant idiot is mixing true caviar with onions etc - that's the way to treat herring's roe or pike's roe (another delicatessen, but not available ready-made). Caviar should be served on a toast (white bread) with a bit of butter (Breton will do, as Vologod is not available in the market) . Caviar might be served with bliny - as Russian bliny are made with yeast dough, the taste is completely different from European crepes. BUT: usually bliny are served not with black, but red (salmon) caviar *.
Caviar goes well not only with chilled vodka, but with dry Russian sparkling wine (or French champagne) - preferrably from "Noviy Svet" distillery, founded by Prince Lev Golitsin.
Because of the costs of caviar and general ignorance beware of fakes. Even in the top restaurant ask to see the jar - the safest is the traditional glass jar (at least you can see the roe). The safest way is to get it open in front of you, and finish it on the spot. When (and if) purchasing caviar, you might need: (a) some rudimental knowledge of the geography of the area; (b) rudimental knowledge of Cyrillic alphabet - or someone else should help you.
In the distant past the sturgeons could be found in many rivers of Europe (that was before WWI & WWII, and before EU, political correctness and multicultural societies), but not anymore. So, if my memory is still OK, the last Baltic sturgeon (a female kept in captivity for breeding) was eaten during the USSR time by the wardens who were supposed to protect it. Thus, if caviar is manufactured in the Baltic states, think twice (too often in the jar there was too much brine and not enough caviar). Nowadays sturgeons are also bred in captivity, and some brands of "caviar" manufactured outside of Russia are available as well - it might be fine, but "Siberian sturgeon caviar" from France to me looks like Perigord truffles from Siberia...
Too much caviar might finish you off (same with foie gras) - if not through bankrupcy, for sure through cholesterol. Still it is well advisable at least to try - before it'll disappear, extinct is forever...
*Red caviar (or "ikura" - from Russian "ikra" - is a component of sushi) is another haute cuisine dish.
And, by the way, toss any book on the Russian cuisine into the dustbin - basically, it's about what the author thought he knows about it...