Diablo – Post 2.0 is Sokahr located in any specific area, or randomly through the Oasis

Total Blacksmith Leveling Cost and Materials

• 593,000 gold
• 50 Page of Blacksmithing
• 50 Tome of Blacksmithing
• 35 Tome of Secrets

Source

Total Jeweler Leveling Cost and Materials

• 140,000 gold
• 20 Page of Jewelcrafting
• 20 Tome of Jewelcrafting
• 40 Tome of Secrets

Source

Drop Rate and place

 - Page of Blacksmithing  - Drops in Nightmare, Hell, Inferno difficulty
 - Tome of Blacksmithing  - Drops in Hell, Inferno difficulty
 - Tome of Secrets        - Drops in Inferno difficulty

 - Page of Jewelcrafting  - Drops in Nightmare, Hell, Inferno difficulty
 - Tome of Jewelcrafting  - Drops in Hell, Inferno difficulty
 - Tome of Secrets        - Drops in Inferno difficulty

These items do not drop in Normal mode

Source

Aside the above information, there are reports about pages droping in ACT IV normal.¹²

I believe is because some monster have a iLv in ACT IV normal equivalent to the early monsters from nightmare (Like the gems, where you get better quality based on the item level), but I couldn't find source to support (or to invalid) this information. (still looking)

Books are always bound to certain potential locations. Some are bound to random dungeon locations so whether you will find some of them is random because it is determined by whether those randomly available locations are generated for you. Also, how many books are present to be picked up in a particular area is also random so if there are more books available for an area than the game generates places to pick them up, it is likely that you may not find all of them. I had to visit Old Tristram/Road 3 or 4 times to get all the books there (picking up 1 or 2 at a time).

Certain sets of books are bound to the same location and groupings of them are always found in a set order (I, II, III, etc.) so the books to do with Old Tristram (Cain's Old Journal, Gillian's Diary, Despina's Journal, Lost Journal, Old DIary) can all be found in Old Tristram or on Old Tristram road and you will always find Gillian's Diary Part 1 before you find Part 2.

Certain book parts will only be available during certain acts (Leah's Journal, Deckard Cain's Journal). The only suggestion I have for this until a complete list is posted for the affected book parts is to check back during each quest in the main story.

If you're missing books for a location after exploring the entire area, the only way to find them is to generate a new map instance for the area (Exit to character select and the Resume) after which you will have to re-explore the area. The trick is figuring out which location holds the book that you are missing.