I found out about Red River from the Anime Planet homepage under "Random Manga", so for me, it was like finding a hidden gem among thousands of other manga. Red River had everything I was looking for in a shojo romance manga, so I hope my following review will help you if shojo romance is your thing.
Story: Red River, in my opinion, has a Cinderella dynamic in which there is a normal girl, a prince, and a wicked stepmother. Yuri is an average girl from Japan, who is transported to 14th Century B.C. by Queen Nakia, the Tawananna of the Hittite Empire. Queen Nakia is hell bent on having her son, Prince Juda, on the throne, but there are many other princes ahead of him. If Nakia is able to slit Yuri's throat, and drain her blood, she will be able to cast a spell to eliminate all of Juda's competition. Through some circumstance, Yuri, who in this world is thought to be the reincarnation of Ishtar, the goddes of war and beauty, ends up meeting and becoming Prince Kail's (3rd prince in line) sole concubine. Kail does this to protect her from Nakia and from there, various plot twists, love triangles, and character development contribute to an excellent story. Kail is able to return her to Japan, provided the following conditions are met: she is wearing the clothes she arrived in, the springs are full of water, and the star of Ishtar is visible in the night sky.
Yuri - Generally, shojo main characters are hit or miss as to whether you like them or not. I liked her, but she came off as a little bit too perfect. Yuri is surprisingly capable of managing wars, infiltrating behind enemy lines, and figuring out the next tactic by Nakia. She excels at being a goody-two-shoes & commander in chief of the Hititte Army. She's strong willed, stubborn, and is able to warm the hearts of practically everyone. She does, however, experience setbacks that make her grow as a character. Yuri is seen by the people as the reincarnation of the goddess Ishtar, which does it's part in contributing to explaining her success and perfect-ness throughout the whole manga.
Kail - Sexy. Mysterious. Politician. Playboy. Before Yuri meets him, he was pretty much banging everyone in sight. He swore to himself he would never have a concubine other than his wife, and would love no other. So when he takes Yuri under protection, it creates a bit of a problem. He is plagued by "I love her, but I can't have her, she doesn't belong to this world", which prevents him from being expressive about his love her Yuri. He can control air, but does not make use of this power.
Nakia - She was a Babylonian princess who was given/"sold" to the Hittite emperor as a concubine after Babylon was conquered in exchange for monetary aid. She felt lonely, and she hated Babylon for forcing her to do this. She can control water through elemental magic and uses this power frequently throughout the story. She is driven by her desire to see her son, Judah, on the throne, so much so that she schemes and causes the death of many people. It is because of her constant scheming that the story is as amazing as it is, it keeps you guessing, and keeps you turning the page because you want to know her plans for what she is doing.
Art - The art was actually pretty good. Given that this was a story about royalty, many of the scenes involves royals with ornate jewelery that, you could just tell required a bit of time to draw.
If you like historical fiction, you will love this because many of these characters are confirmed to have existed. The manga actually plays out battles that took place during this time, as well. Some of the more well known historical figures, such as Ramses, Homerheb and Nefertiti make appearances. The story arc with Kail's brother, Zannanza, is actually documented to have occured: http://en.wikipedia.org/wiki/Zannanza
Very good read, highly reccommend reading this.