Hmmmm... some stuff that was good?
Manga: Same as steamrick I recommend Mx0. Whilte it is is a pretty old manga which had some touches of the classical Harem genre, it never really went deep into it as some other series did. Has glorious Xanathos Gambits and fun characters, still sad that it got dropped and the author had to write an ending earlier.
Ai Kora, straight up Harem Comedy at first glance, but a good bit deeper than expected. All the characters have their own past and personality which are touched upon. Painful parts, happy parts and an Ending that you don't expect to see in most of These series.
A Fairy Tale for the Demon Lord.... this one is interesting, if a bit confusing at times. Starts with a Young warrior trying to free a princess if I remember right. It is the Story of how this Knight is betrayed and forced to become the new Demon Lord, his past and future and the Horror of Destiny.
Tower of God is pretty good, though I have not been checking through the latest chapters. Growing up stories of the Boy called 25th Baam (Night if I remember right) and how he climbs the Tower to look for a Girl called Rachel/Rahel. Very interesting worldbuilding and Setting, the author loves marine life, so that has a good bit of influence in the creation.
Mushigbugyou is a good Shounen, nothing world breaking, but solid Story and interesting if somewhat simple at times, characters. Has an Anime which is already further than the Manga is translated, so you could check that out first. I suggest at least looking into the Manga to compare it. There are two Versions of the Manga, one a first Version and a Rewrite of some sorts which continued while the former ended at I think a dozen chapters?
D-Frag, glorious bullshit chaos and randomness. Think Luna Lovegood from HP, but drunk and high. And all the characters except the main character and his sisters are crazy like that and do bullshit at times. Seriously, the series is absolutely hilarious and the characters always give me a laugh... and the puns.... has an Anime which is pretty good and has a gloriously hilarious opening. Kinda nonsensical though.
Noucome is also good, not as hilarious but has some good parts and the Unlimited Blade Works joke will forever be in my Memory. Has an Anime, never really saw an manga, though I think one may be around.
The World God Only Knows for more Xanathos Gambits and deeper characters that you will likely grow quite fond of. Pretty interesting interactions, cool Story and Background even if there is some stuff that never gets explained. Already completed, has good Anime and great character Songs and such.
I also like Sankarea which steamrick suggested, pretty solid Story with fun stuff and the romance well made. Not everyone liked the ending apparently, but it cannot be helped with something that has some serious overtones of Horror and tragedy that not everyone can be happy.
Books? Hmmm.... Secrets of the Immortal Nicholas Flamel has awesome Research put into it and great characters with Scathach from that book always being what I think of,.
The "Black Magician Trilogy" and related books are also good with a great writing style and having the ability to let you easily immerse into them. The main character is fun and plot twists aren't obvious at all....
Maybe the "Mara and the Firebringer" series of books? There is a movie to the first book out which is apparently pretty fun, though I am not sure whether it came out in English. The book series is originally german too, so no clue.
