Put together a list of all the Amazon Kindle e-book versions of H!P & related idols already available for purchase or announced to be released by the end of the month. It's a rather large list so I put it under a spoiler.
Abe Natsumi
- Écru (2006)
- Cám Ơn (2007)
- End Of Summer (2008)
- Natsu-Mi (2010)
- Subway (2012)
Funaki Musubu
- MUSUBU (2017)
- MUSUBU16 (2018)
Ishikawa Rika
- Oui, mon amour (2006)
- Abyuu (2007)
- Karen (2009)
- 24 Twenty Four (2009)
- Lucky☆ (2011)
- Hana Gokoro ~hanagocoro~ (2012)
Kikkawa You
- YOU (2011)
- YOU21 (2013)
Kudo Haruka
- Do (2012)
Kusumi Koharu
- Sugar Doll (2009)
- moment (2017)
Mano Erina
- Mano Erina (2009)
- Tengoku no Door (2010)
- Mano Days ~Hatachi no Hatsukoi~ (2011)
- MANO DATE (2012)
Michishige Sayumi
- 20sai 7gatsu 13nichi (2009)
- La (2010)
- Sayuminglandoll (2011)
- Mille-feuille (2013)
Miyamoto Karin
- Karin (2014)
- Karin sixteen (2015)
- SUNFLOWER (2016)
- KAKUSEI (2018
Morning Musume
- Haikei, Haru-senpai! ~Higashi-Azabu Koukou Hakusho~ (2017)
Niigaki Risa
- ASCENSION (2012)
Oda Sakura
- Sakura Moyou (2016)
- Sakura Breeze (2017)
- Sakura no Kisetsu (2019)
Sayashi Riho
- Sayashi Riho (2011)
- Un Deux Trois (2012)
Suzuki Airi
- Airi (2007)
- 6gatsu no Kajitsu (2008)
- Aoiro (2009)
- Toukobi (2010)
- Meguru Haru (2011)
- OASIS (2011)
- Kono Kaze ga Suki (2012)
Takahashi Ai
- Watashi (2009)
- Katachi (2010)
- LOVE NO.10 (2011)
- Ai Ai Ai (2011)
Wada Ayaka
- Wada Ayaka 16 (2011)
- aya (2012)
Yajima Maimi
- Maimi (2007)
- Sou Sola (2008)
- 17 (2009)
- Tabioto (2011)
- hatachi (2012)
I was surprised there were so many so fast since the announcement of this initiative. So far it seems they've tied old releases to a girl coming out with a new photobook (Sakura, Musubu, Karin) alongside a smattering of older releases mostly from what could arguably be said to be the more popular girls who released photobooks, or were known for releasing them (Ishikawa, Abe, Takahashi, Mano, Airi,...).
Curiously no Fukumura Mizuki or Makino Maria yet. These are also all pure Wanibooks releases. None of the in-house Odyssey or Odyssey & Wanibooks joint releases were included. Kusumi's Moment is included but I believe it was already available before all of this being that it was released after she left UF and is published by Futabasha. Also none of the H!P members that are currently, shall we say 'blacklisted' in public life, are included. They're all from girls that are currently active and in good standing or have retired of the idol life with no issues.
This is good stuf so far, I hope they manage to include as many of them as they can.