Serious Mass or Mass Gainer contain loads of carbohydrates. You can't build muscles on carbs. Muscles are made of protein and fat. Whey protein is a better choice. Only soy protein would make your hormone goes haywire. Whey protein is perfectly safe for long term consumption.

For a skinny guy to look bigger, you need to eat more, and hit the gym at least twice a week to do heavy weights. Whey protein can be taken about 15 minutes before the workout. Mass gainers are useful if you cannot add more food into your diet, and need to meet that extra calories count, personally I would say not more than 600 calories should come from a mass gainer for health purposes.

whey protein will provide you with an extra protein that your body needs to build muscle and in term of absorption ,it also fastest among other type of protein such as meat,chicken, egg, etc.

Mass gainer may also contain whey protein with an extra carbohydrates to support the needs of higher calories for your body to gain weight. it is mostly used for someone who want to increase mass/bulking etc. If you want to compare between this two supp, the different is the calories of each supp. Mass gainer one serving would be around 1200 cal meanwhile one serving whey protein = 200 cal

You can't escape from solid food. I've been in your shoes. Eat more for the first week, you will feel really bad, but after that, the body gets used to it and you'd feel hungry naturally. Once you reach your true solid food maximum, then start considering liquids such as soft boiled eggs, and as a final resort, weight gainer.

The reason for eggs being such a celebrity is because not only is it nutrient dense, it is also high in calories and is easily consumed. Just soft boil 4 eggs, add some white pepper and soy sauce to taste, and drink it. Getting kampung eggs helps a lot with the palatability.