Kenshi research: prerequisites and materials
A research topic asks for three separate things: topics researched before it, materials it consumes, and a research level. Light Post shows all three. It needs Indoor Lighting, it consumes a 
Book, and its record sits at level 2, the level Tech Level 2 raises the research to. Finishing it opens the 
Light Post I.
Prerequisite, cost and unlock
A prerequisite is a topic that has to be researched first. A cost is material the bench takes when the topic is researched. An unlock is what the finished topic adds to the build menu. The two topics on the way to a light post show each of them:
- Tech level
- 1
- Materials
- 1 × BookWhere to buy
- Unlocks
Ceiling Fan Lamp, 
Ceiling Lamp, 
Electrical Torch Post
- Tech level
- 2
- Requirements
- Indoor Lighting
- Materials
- 1 × BookWhere to buy
- Unlocks
- Light Post I
Indoor Lighting has no prerequisite, but that does not make it researchable in a new game. A start that hands over no Book and no bench leaves it waiting for both.
Research levels
The level is not a prerequisite edge. Every topic's record carries a level number, and a short run of topics raises the research level itself, each opening the next research bench:
| Name | Tech level | Materials | Unlocks |
|---|---|---|---|
| Tech Level 2 | 1 | 6 × Book |  Research Bench II |
| Tech Level 3 | 2 | 10 × Book |  Research Bench III |
| Tech Level 4 | 3 | 4 ×  Ancient Science Book |  Research Bench IV |
| Tech Level 5 | 4 | 8 × Ancient Science Book |  Research Bench V |
| Tech Level 6 | 5 | 2 ×  AI Core |  Research Bench VI |
Tech Level 2 needs Small House before it, so the road to a level 2 topic such as Light Post runs through a house and the books that level costs, not only through its own prerequisite.
Getting the materials
A Book can be bought. The supplier lookup beside each cost lists the towns, shops and factions whose stock lists carry the item. A stock list says a shop can carry it, not that one is on the shelf today. A map that reveals a town reveals the town, not a book inside it.
Some topics are marked blueprint only in their record. They are learned from a blueprint rather than taken from the tree, and the research tree lists where each of those blueprints is sold.