Craps is a wonderful game because of the unique characteristics it has that no other table game can really claim to possess. For starters, there is a certain amount of energy at a craps table that you will never find at any other table in the casino. The reason for this is that the craps table has people making the fortunes of other people at the table and for that reason successful wagers are far more emotionally fulfilling and therefore lend themselves to a more jovial celebratory mood. In addition to the energy issue, craps is home to what is perhaps the best bet you will ever find in the casino in an overall sense. The bet is known as the pass line bet and it has the lowest house edge of any bet that is universally available. There is even an odds bet later on in the craps game where there is no house edge whatsoever, but it is available less frequently and much harder to understand strategically than the pass line bet. For this reason, many new players to the casino end up starting with the pass line bet in craps.
Overall however, craps availability in Las Vegas is less than either blackjack or roulette. The good news is that all the major casinos in Las Vegas (i.e. the ones that are discussed on this website plus all of the major ones that you hear by name all the time) will have multiple craps tables and for that reason if you do your gambling at a major casino, you will not really have to worry about the availability issue. However, with some of the smaller casinos in Vegas you will find craps availability start to drop off dramatically. While there is probably not a single casino that does not have access to a craps table that they can bring out if the demand exists for it, there are at the same time many casinos that do not operate craps tables around the clock because of the lack of demand for the game their particular clientele happens to display. These would be mostly blackjack and slots casinos however and for that reason you should probably not walk into one expecting to find a craps table anyway.
There are no real variants of craps beyond the normal craps game that people are used to seeing. For that reason, discussing the variant of craps that is available in the casino is not really worthwhile. The one thing you should keep in mind when thinking about craps variants or any minute changes that might happen in the game however is the fact that the odds should be displayed right there on the board, something that does not happen with blackjack (beyond insurance payments) or roulette. This makes craps almost by definition a game that is easier for people to learn because the most important rules (the odds) are already available to them as they continue to play. This also contributes to the overall sense of high energy that the game has.
