As should be obvious from this website, I'm a huge comic book fan. One of the offshots of that interest is Power Rangers. I didn't watch the series when if first came out but got interested in it around the Ninja Storm and DinoThunder seasons. I've since watched all of it since Turbo and much of the early Angel Grove years. Personally, I find aspects of the early seasons a bit difficult to watch at times. Over the years the series has changed and grown considerably. The series is leveraging more of the Sentai storylines and ideas which is both good and bad.
I started watching the Sentai series with Abaranger (which was the basis for DinoThunder). I've been hooked on the Sentai shows ever since.
Over in Japan there are books for each Sentai series. I'm not entirely sure when these books started getting published. Starting with Dekaranger, a single book a year was no longer enough room to cover the year long series so they now do two books for each season.
While it is not entirely trivial to get copies of these books here in the USA, it is possible. I've been able to build a library of all of the ones published so far for the sentai shows that have been adapted into Power Rangers. The text is all in Japanese but these books are mainly visual reference books and the text is limited to captions for the photos.
Dengeki Sentai Changeman
Choujin Sentai Jetman
Kyouryuu Sentai Zyuranger
Gosei Sentai Dairanger
Ninja Sentai Kakuranger
Chouriki Sentai Ohranger
Gekisou Sentai Carranger
Denji Sentai Megaranger
Seijuu Sentai Gingaman
Kyuukyuu Sentai GoGo V
Mirai Sentai Timeranger
Hyakujuu Sentai Gaoranger
Ninpuu Sentai Hurricaneger
Bakuryuu Sentai Abaranger
Tokusou Sentai Dekaranger
Mahou Sentai Magiranger
GoGo Sentai Boukenger
Juken Sentai Gekiranger