I have it it is an old book and I don't think there is any new information that a collector at your level would find useful.
But if you would like any specific information I can dig it out and would be happy to tell you anything at all. If i remember correctly it is full of line drawings and not a single actual photograph of a helmet.
Im sure it was helpful back in the day and i remember reading it years ago but with the reference books out today with hundreds of photos of original items both inside and out this one shows it's age.