star wars - What are the significant discrepancies between the official novelization by Foster and the movie for The Force Awakens

Star Wars - Episode VII: The Force Awakens has received an official novelization from Alan Dean Foster.

What significant differences to plot points, characters, etc, are there between the novelization and the movie?

I'm looking for things that could make a big difference (in and/or out of universe), not costume differences, slight differences in character descriptions (hair style, eye color, height, etc), or the like.

Answer

Missing scenes in the script/film

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  Han discusses BB-8's map on the Falcon and mentions that he can actually recognize a nebulae on it. This implies in the books that he knows the general area where the map points to (leading to obvious question of, why do we need the rest of the map in R2D2?). We don't get that in the film or the script.

  
  


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  Leia discussing with her envoy sending her to Hosnian Prime. It doesn't change the plot, but it offers a major clarification into the political situation between Republic and Resistance.

  
  

Differences

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  In the film GA-97 takes the initiative to contact the Resistence about BB-8. In the novelization, C-3PO activates a whole network of droid informers first, realizing that BB-8th long range communicator was turned off by mistake.

  
  


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  There are some differences in the Force Vision, discussed in detail here. Some of them may imply important plot differences regarding Rey's past or parentage

  
  


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  The mechanics of how Starkiller base works differs significantly. In the novelization, it works on Dark Energy and merely uses solar power in a "normal" way, to power Dark Energy collector. In the film it looks like it literally eats/destroys its star, in order to fire. This is confirmed in WGA script:

  
  

  
  

  A vast view of the planet -- a MASSIVE SOLARVAC ARRAY surrounds a port TEN MILES IN DIAMETER. MILLIONS OF PANELS turn on the ARRAY -- a wave of BRILLIANT REFLECTIONS. Suddenly, like a planetary-scale TESLA COIL LINE OF ENERGY, THE POWER OF THE SUN begins to TRAVEL DOWN to the Starkiller Base planet.

  
  
  

  
  

  and in Finn's briefing

  
  

  
  

  FINN It uses the power of the sun. As the weapon is charged, the sun is drained until it disappears.

  
  

  
  

  and

  
  

  
  

  They follow Finn on the snowy hike. On the horizon, THE LASER SIPHON SHOOTING INTO THE SKY, SLOWLY SUCKING THE SUN DRY.
  INT. STARKILLER BASE - CONTROL ROOM - DAY
  Technicians at work, the SUN SUCKING seen in the window behind him.

  
  
  

  
  

  With all due respect to Mr. Abrams, the film's choice is far worse plot wise.

  
  


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  The destruction also is different. In the novelization, there's only 1 target (Hosnian Prime), and the rest of Hosnian system is destroyed by a blast from the nova that the planet became. In the film, it looks like individual "sub-rays" of the weapon separate and hit other planets, and the same is hinted at in WGA script.

  
  

  
  

  At a massive distance we see PLANETS THE REPUBLIC CAPITAL SYSTEM -- INCREASINGLY LIT, THEN POWERFULLY HIT BY THE VAST FIREBLAST WHICH OBLITERATES IT ALL!

  
  

  
  


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  Far smaller difference: in the film, JB-007 trooper she tries to Jedi Mind Trick sasses back at her at first (I'll tighten those restraints, scavenger scum!). In the book, he merely doesn't react at her first attempt. Which means that line by 007 may have been an ad-lib.

  
  

Bonus round: Differences implied by prequel book

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  The film left a very strong impression that Finn is a half-@ssed Stormtrooper, bottom of Sanitaton barrell. The prequel clearly shows that he was awsome, 1% of his training class, leadership candidate being groomed personally for advancement by Captain Phasma.

  
  


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  The film strongly implies that he had exibited NO previous deviations from other stormtroopers and his sudden empathy explosion is unexpected (and possibly triggered by the comprade stormtrooper dying). The prequel clearly explains that this is NOT the case, that he has struggeled with empathy for a long time, and Jakku was Phasma's last chance for him to turn from a soft-hearted plushie into a real heartless stormtrooper who can shoot at real people, not just training simulation targets.