Yes,book it now!
Ours was a solo traveller trip and everyone got along just fine. So if you are fretting about a first trip on your own,dont worry you will soon make friends. Our trip was in March and the temperature was pretty perfect. Also we were told - and the fact bears this out- that the chance of seeing a tiger was higher around now as they were more active (we also spotted a leopard ).
Money-wise, food and excursions etc. were quite cheap and most people seemed to spend less than they had expected.
Our tour leader arranged for us to get our currency in Jaipur where the rate is better than at Delhi airport. It is a good idea to keep a wad of 10 rupee (15p) notes to give to toilet attendants etc. Also,remember to tell your bank you are off to India as lovely Lloyds TSB blocked my card at the ATM,even though I have used it abroad on numerous previous occasions. They did, however re-imburse me the £16 mobile phone bill I incurred speaking with them though. It might be a good idea to test it out early in the trip and avoid running out of cash temporarily.
There is necessarily a fair amount of time spent in the coach,but this is never dull and is interspersed with comfort breaks,lunch breaks etc .
The food was pretty good everywhere, thanks in no small part to Sanjay's local knowledge.
It is sensible to take hand gel to use frequently, which minimises the chance of having to check out the sanitation at short notice too often. In fairness the loos weren't too bad in most places.