query on powershell script that downloads the Microsoft Ebook Giveaway books - powershell

Question

Got a whatsapp message that Microsoft is giving away free ebooks from the below url.
URL : Microsoft Ebook Giveaway
To download all the books in one go, the following powershell script was used, which is available in the same url.
Now my problem is, if I run the powershell script as a whole, it is not throwing any error. All the books from the url gets downloaded to a single location in my computer.
But if I try to run the script line by line to understand what each statement does, it is giving the following error when the , $bookList = Invoke-WebRequest $downLoadList gets executed,
Now to resolve this error, there are many others posts in stack overflow, that passes the username and password to overcome this error. Those scripts / solutions are not working at my end.
More than the error, why is it, that the script runs without any errors/issues when I execute the full script, but throws an error when I execute line by line ?
Any inputs on the nature of execution or helpful tips in overcoming the error will be useful... Thank you.
Error :
Invoke-WebRequest : (my ip number )
Credentials are missing.
Make sure to specify a domain with your username
This website has been blocked by a cyber security policy
and SecureWeb does not currently support web exceptions
If you have an exception, copy the link below into a new tab
http://ligman.me/2tk1D2V
At line:1 char:13
+ $bookList = Invoke-WebRequest $downLoadList
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+ CategoryInfo : InvalidOperation: (System.Net.HttpWebRequest:HttpWebRequest)
[Invoke-WebRequest], WebException
+ FullyQualifiedErrorId : WebCmdletWebResponseException,Microsoft.PowerShell.Commands.
InvokeWebRequestCommand
PowerShell Script :
###############################################################
# Eric Ligmans Amazing Free Microsoft eBook Giveaway
# https://blogs.msdn.microsoft.com/mssmallbiz/2017/07/11/largest-free-microsoft-ebook-giveaway-im-giving-away-millions-of-free-microsoft-ebooks-again-including-windows-10-office-365-office-2016-power-bi-azure-windows-8-1-office-2013-sharepo/
# Link to download list of eBooks
# http://ligman.me/2tk1D2V
# Thanks David Crosby for the template (https://social.technet.microsoft.com/profile/david%20crosby/)
#
# Modified by Robert Cain (http://arcanecode.me)
# Added code to check to see if a book was already downloaded,
# and if so was it the correct file size. If so, the book
# download is skipped. This allows users to simply rerun the
# script if their download process is interrupted.
###############################################################
# Set the folder where you want to save the books to
$dest = "I:\new_microsoft\" # Make sure the file path ends in a \
# Download the source list of books
$downLoadList = "http://ligman.me/2tk1D2V"
$bookList = Invoke-WebRequest $downLoadList
# Convert the list to an array
[string[]]$books = ""
$books = $bookList.Content.Split("`n")
# Remove the first line - it's not a book
$books = $books[1..($books.Length -1)]
$books # Here's the list
# Get the total number of books we need to download
$bookCount = $($books).Count
# Set a simple counter to let the user know what book
# number we're currently downloading
$currentBook = 0
# As an option, we can have it log progress to a file
$log = $true
if ($log -eq $true)
{
# Construct a log file name based on the date that
# we can save progress to
$dlStart = Get-Date
$dlStartDate = "$($dlStart.Year)-$($dlStart.Month)-$($dlStart.Day)"
$dlStartTime = "$($dlStart.Hour)-$($dlStart.Minute)-$($dlStart.Second)"
$logFile = "$($dest)BookDlLog-$dlStartDate-$dlStartTime.txt"
}
# Download the books
foreach ($book in $books)
{
# Increment current book number
$currentBook++
try
{
# Grab the header with the books full info
$hdr = Invoke-WebRequest $book -Method Head
# Get the title of the book from the header then
# make it a safe string (remove special characters)
$title = $hdr.BaseResponse.ResponseUri.Segments[-1]
$title = [uri]::UnescapeDataString($title)
# Construct the path to save the file to
$saveTo = $dest + $title
# If the file doesn't exist, download it
if ($(Test-Path $saveTo) -eq $false)
{
$msg = "Downloading book $currentBook of $bookCount - $title"
$msg
if ($log -eq $true) { "`n$($msg)" | Add-Content $logFile }
Invoke-WebRequest $book -OutFile $saveTo
}
else
{
# If it does exist, we need to make sure it wasn't
# a partial download. If the file size on the server
# and the file size on local disk don't match,
# redownload it
# Get the size of the file from the download site
$dlSize = $hdr.BaseResponse.ContentLength
# Get the size of the file on disk
$fileSize = $(Get-ChildItem $saveTo).Length
if ($dlSize -ne $fileSize)
{
# If not equal we need to download the book again
$msg = "Redownloading book $currentBook of $bookCount - $title"
$msg
if ($log -eq $true) { "`n$($msg)" | Add-Content $logFile }
Invoke-WebRequest $book -OutFile $saveTo
}
else
{
# Otherwise we have a good copy of the book, just
# let the user know we're skipping it.
$msg = "Book $currentBook of $bookCount ($title) already exists, skipping it"
$msg
if ($log -eq $true) { "`n$($msg)" | Add-Content $logFile }
}
}
} # end try
catch
{
$msg = "There was an error downloading $title. You may wish to try to download this book manually."
Write-Host $msg -ForegroundColor Red
if ($log -eq $true) { "`n$($msg)" | Add-Content $logFile }
} # end catch
} # end foreach
# Let user know we're done, and give a happy little beep
# in case they aren't looking at the screen.
#"Done downloading all books"
#[Console]::Beep(500,300)