These anime share many of the same key staff. The first thing you'll notice are of course the character designs, which are done by Yoshitoshi ABe. Both anime also share the same themes.
Similar dark tones. They're both slow paced. They both focus a lot on the visuals that create a haunting atmosphere. Same character designer.
Both are low-pace dark cyberpunk animes which can be at times focused on visual communication.
Quite similar in terms of artistic quality. Both are deeply experimental, avant-garde anime that make you question, rethink and analyze a lot of things that happen in your life. They broaden your mind and are incredibly fulfilling experiences. Viewing these should be compulsory on your way through adolescence towards maturity.
Same original creator, almost same style, same strong feelings, same masterpieces... Do you still need more?
Definitely most similar anime in atmosphere of all listed here, should be at first place imo. Similar melancholic, lonely style if thats what you are looking for although its not the same thing... There is nothing like lain. ;)
If you read manga and like steam/cyber punk try blame! manga too.
Has that same drug-like feeling. These two series like to make you blink twice and almost question what you're watching. They're haunting and share the same atmosphere... If you liked one, definitely try the other.
Lain is like first episode of Texhnolyze, but longer. There are a lot more SPEAKING going on, but nothing too coherent. A lot of atmoshpere. Same writer, same dark tone, same style of storytelling (if you can call it that), same pretentiousness... Well, same writer really sums it up.
Both series are cyberpunk, they also have similar themes, style, and a lot of somewhat abstract segments.
Both use ABe's unique artstyle and deal with heavy themes. Texhnolyze is ultimatly darker than Lan in every way, but their atmosphere and pacing are very simular
Mysterious wired animes and almost share everything like character design and dark background.
The main characters are lonely guys who trying to understand the surrounding world
Both have philosophical themes, both are made by the same creators, both have cyberpunk plots, both are very dense and have good characters