There is additional functionality that allows you to analyze the raw text data
As it is divided to 100 fragments you may use the following to download it as a first step and continue from there
Table[URLDownloadSubmit[
"http://commondatastorage.googleapis.com/books/syntactic-ngrams/eng/\
nodes." <> IntegerString[n, 10, 2] <> "-of-99.gz",
"~/Downloads/" <> IntegerString[n, 10, 2] <> ".gz",
HandlerFunctions -> <|"TaskFinished" -> Print|>], {n, 0, 98}]
best