Planetes, Toshokan Sensou Recommendations
Both have a somewhat earnest and idealistic female as the leading character who tries to change the world they live in. Both also have a relatively smaller close-knit group of characters. The male lead in each series is shorter than average and have hot-heads. The art styles and character designs deviate from regular anime styles and both these shows have political undertones.
Both series feature an endearing, enthusiastic airhead of a protagonist making her debut in her dream job with the support of a very colorful (and equally endearing) cast of strong characters. While in one case the goal is to protect books (and therefore culture and knowledge) and in the other it is the environment that is at stake, Kasahara (Toshokan Sensou) and Tanabe (PlanetES) share a same ideal and a similar approach in how to defend it. They also encounter the same hardships and embark on similar journeys, which makes for great character development and emotional involvement in both series.
Oh, and last but not least
The main characters of Planetes, Ai Tanabe and Hachirota Hoshino, resemble those of Toshokan Sensou, Iku Kasahara and Atsushi Doujou.
Ai Tanabe is working hard to strive her goal, same with Iku Kasahara, and they both are stubborn when it comes to what they believe in. They will fight for their views. They also share the same pride for their work. Ai Tanabe, as well as Iku Kasahara, both share the same feelings they have for their respective main male characters.