There is nothing unclear about "55 hours of battery life with light on". That is a lot of battery life! You could go almost a month reading two hours a day, with the Glo feature on... and that's a LOT of reading.
What doesn't make sense is the "One month with the light off" statement. The device surely uses less power with the light off. The only explanation I can think of is this means one month of continuous use (1 month x 30 days x 24 hours a day = 720 hours). Although I doubt this is the case because that's a crazy long amount of battery life.
I wish manufacturers would simply state their battery life in terms of hours of continuous use instead of this "1/2 hour of reading per day" crap.
Incidentally, I have no idea if the Kobo Glo will support landscape mode... but if it doesn't, I'm afraid I'll end up sticking with Amazon and getting a Paperwhite.